WASHINGTON  – The Senate is poised to add $2 billion to the popular “cash-for-clunkers” program after lawmakers agreed to vote on the government car incentives and give shoppers until Labor Day to make a deal on more energy-efficient models.

The White House has estimated that tripling the $1 billion program could pay for 500,000 more new-car sales, giving automakers a late-summer boost after months of ragged business. The Obama administration has said the program would go broke by Friday without Congress’ approval of the extension.

Senate Majority Leader Harry Reid said Democrats and Republicans had agreed to vote on the plan later Thursday after the formality of considering potential changes to the House-passed version of the bill. None of those amendments is expected to pass.

Senate approval of the House version would send the legislation to the White House for President Barack Obama’s signature and assure consumers there will be no interruption in the program that provides up to $4,500 in rebates and helped rescue car dealerships from lagging sales.

“There’s a significant majority that want to move forward with this legislation,” said Reid, D-Nev., who nonetheless agreed to bring up amendments as a goodwill gesture to those who otherwise might try to delay a final vote on the House-passed version.

The proposed changes that will receive an airing include placing an income limit on those benefiting from the vouchers, terminating the Troubled Asset Relief Program and requiring the government to sell off its shares in Michigan automakers General Motors Co. and Chrysler Group LLC.

Sen. Tom Harkin, D-Iowa, for example, wants the vouchers limited to individuals earning less than $50,000 a year or joint filers earning less than $75,000.

As the bill stands, Microsoft founder Bill Gates can get $4,500 to buy a new car, Harkin said Thursday. “You have to ask,” Harkin said, “is this a wise way to spend limited amounts of money?”

Any Senate changes to the bill would require another vote in the House, something that couldn’t take place until the House returns in September from a monthlong recess. The Senate is taking its break following votes on the car incentives and the confirmation on Supreme Court nominee Sonia Sotomayor.

Republican opponents have conceded they are unable to force all of the changes they want or to block the House version of the bill. But they still grumbled about more government handouts to the private sector.

Sen. John Thune, R-S.D., called the bill an example of “Congress choosing winners and losers among industries.”

The government said Wednesday that more than $775 million of the $1 billion fund had been spent, accounting for nearly 185,000 new vehicles sold. Administration officials estimate the extra funding will last into Labor Day.

Car companies credit the clunkers program with driving up sales. Most consumers are buying smaller, more fuel-efficient vehicles through the program, according to a list of the top-10 selling cars released by the government.

Among manufacturers, General Motors Co. had the largest share, accounting for 18.7 percent of new sales; followed by Toyota Motor Corp., with 17.9 percent; and Ford Motor Co., with 16 percent. Detroit automakers represented 45.3 percent of the total sales while Japan’s Toyota, Honda Motor Co. and Nissan Motor Co. accounted for 36.5 percent.

The Toyota Corolla is the top-selling vehicle on the list, followed by the Ford Focus, Honda Civic, Toyota Prius and the Toyota Camry. There is one SUV on the list, the Ford Escape, which also comes in a hybrid model that can get up to 32 miles per gallon. Six of the top-10 selling vehicles are built by foreign manufacturers, but most are built in North America.

The prospect of extending the clunker program is causing automakers to rethink their production schedules and perhaps bring back laid-off workers.

GM’s manufacturing team was working on a production increase Thursday morning, Tom Stephens, vice chairman of product development, said in an interview.

GM has had spot shortages of compact and midsize cars, which have been popular with people trading in clunkers, Stephens said. The company also reported an increase in sales of the Chevrolet HHR small sport utility.

“Consumer confidence is really what you need here,” Stephens said. “It’s hard for them if they don’t know if they have a job or a for-sure paycheck to go out and make a major purchase, so I think this is kind of jump-starting some things.”

Hyundai Motor Co. already has added a day of production at its Montgomery, Ala., factory, while Ford Motor Co. is considering a production increase.

WASHINGTON – President Barack Obama will issue new fuel efficiency standards and pair them with a broader goal of reducing pollution from vehicle tailpipes, marking the first time limits on greenhouse gases will be linked to federal standards for cars and trucks.

Officials familiar with the administration’s discussions say Obama will unveil the new standards on Tuesday. The officials spoke on condition of anonymity because the official announcement had not been made.

California, 13 other states and the District of Columbia have urged the federal government to let them enact more stringent standards than the federal government’s requirements. The states’ regulations would cut greenhouse gas emissions by 30 percent in new cars and trucks by 2016.

Officials said Tuesday’s announcement moves toward the 30 percent goal by 2016, starting with model years 2011 and beyond.

The proposal is expected to coordinate two separate standards for fuel efficiency and greenhouse gas emissions from vehicles, aiming for cars that achieve higher miles per gallon and have lower polluting air conditioning systems, said Roland Hwang, the vehicles policy director for the Natural Resources Defense Council. The environmental group has discussed the upcoming changes with the White House in recent weeks, he said.

Hwang said he expected the greenhouse gas standard would be set to an equivalent of nearly 35 miles per gallon for the vehicle fleet by 2016.

A 2007 energy law requires car makers to meet at least 35 mpg by 2020, a 40 percent increase over the current standard of about 25 mpg. Passenger car requirements have remained unchanged at 27.5 mpg since 1985, drawing complaints from environmental groups that the government has been slow to push automakers to produce more fuel-efficient vehicles.

Automakers have sought a single, national standard and argued that a patchwork of regulations will hurt an industry already in dire economic straits and do little to address global warming.

Obama’s move also would effectively end litigation between states and automakers, who sought to block state-specific rules. The new federal rules would prompt automakers to drop their lawsuit. Two car companies who have been part of the litigation, General Motors Corp. and Chrysler LLC, have received billions in government loans during a dramatic downturn in car sales and weakened economy.

A March 2008 decision prevents states from setting their own limits on greenhouse gas emissions from automobiles, but Obama has ordered the U.S. Environmental Protection Agency to reconsider the ruling. California and the other states have asked the EPA for permission to set a standard for reducing greenhouse gases from automobiles.

Michigan Gov. Jennifer Granholm, a Democrat who is being considered for the Supreme Court vacancy, will be at the White House for the Tuesday event on auto emissions standards, said an administration official who spoke on condition of anonymity because details of the event had not been announced.

California Gov. Arnold Schwarzenegger, a Republican, will be in Washington for an announcement on California’s request regarding federal auto emissions standards, Schwarzenegger spokesman Aaron McLear said. He declined to elaborate.

WASHINGTON – President Barack Obama ordered the government Monday to re-examine whether California and other states should be allowed to have tougher auto emission standards, a clean break from Bush administration policy.

Jumping into the seemingly never-ending national energy debate, Obama also directed his administration to get moving on new fuel-efficiency guidelines for the auto industry in time to cover 2011 model-year cars.

“For the sake of our security, our economy and our planet, we must have the courage and commitment to change,” Obama said in his first formal event in the ornate East Room of the White House.

“It will be the policy of my administration,” he said, “to reverse our dependence on foreign oil while building a new energy economy that will create millions of jobs.”

California and at least a dozen other states have tried to come up with tougher emission standards than those imposed by the federal government, but Obama said that “Washington stood in their way.” The president wants the Environmental Protection Agency to take a second look at a decision denying California – and the other states that want to follow its model – permission to set its own tailpipe emission standards.

More broadly, Obama sought to show he was not waiting to put his stamp on energy policy, which has both near-term implications on the sagging economy and long-range effects on pollution, climate change and national security.

“Year after year, decade after decade, we’ve chosen delay over decisive action,” Obama said. “Rigid ideology has overruled sound science. Special interests have overshadowed common sense. Rhetoric has not led to the hard work needed to achieve results – and our leaders raise their voices each time there’s a spike on gas prices, only to grow quiet when the price falls at the pump.”

The Clean Air Act gives California special authority to regulate vehicle pollution because the state began regulating such pollution before the federal government got into the act. But a federal waiver is still required; if the waiver is granted, other states can choose to adopt California’s standards or the federal ones.

In 2007 the Bush administration’s Environmental Protection Agency denied California’s waiver request, gaining praise from the auto industry but touching off a storm of investigations and lawsuits from Democrats and environmental groups who contended the denial was based on political instead of scientific reasons.

Obama on Monday directed the EPA to re-examine the decision. That does not yet overturn anything. But still, the states’ wanting their own power considered it a victory.

“The federal government must work with, not against, states to reduce greenhouse gas emissions,” Obama said. He added: “The days of Washington dragging its heels are over. My administration will not deny facts; we will be guided by them.”