WASHINGTON (AP) — After years of procrastination, the White House and Congress have suddenly boosted a long-term plan to improve the nation's roads, bridges and transit systems to the top of the political agenda.

This week the House and Senate are set to take up vastly different bills providing a blueprint for shoring up the nation's aging transportation system. Lawmakers are driven in part by a desire to show voters a major accomplishment in an election year when regard for Congress is at rock bottom. They are pitching the bills as jobs generators, although it may be more accurate to say they preserve jobs that might otherwise be lost if Congress doesn't find a way to keep highway and transit programs solvent.

President Barack Obama chimed in Monday with his own plan to spend nearly half a trillion dollars over six years on transportation infrastructure. But the president's plan is so much grander than anything Congress is likely to go along with that the administration has swung its weight behind the Senate bill, a bipartisan plan that more modestly proposes to spend $109 billion over less than two years.

House Republicans have proposed spending about $260 billion over nearly five years, but the bill is drawing fire from so many quarters that the ability of Speaker John Boehner, R-Ohio, to muscle the measure through to passage is in doubt. To build support with tight-fisted tea partiers for such a large spending bill, GOP leaders added sweeteners designed to appeal to conservatives, such as expanded offshore oil and gas drilling, approval of the controversial Keystone pipeline and a requirement that federal employees pay more toward their pensions.

The bill's treatment of mass transit programs has riled urban lawmakers, including New York and Chicago metro-area Republicans who may wind up voting against the bill. It eliminates the guarantee of a portion of federal gasoline and diesel tax revenues for transit, leaving programs vulnerable to future budget cuts.

"If you are a Republican from a city that has mass transit, how can you vote for this and go home?" said Rep. Jerrold Nadler, D-N.Y., who is sponsoring an amendment to restore a portion of fuel tax revenues for transit. Seven Republicans have co-sponsored the amendment.

And six GOP lawmakers have sent a letter to Boehner and other GOP leaders saying the transportation bill will stand a better chance of passage if provisions opening leases in the Arctic National Wildlife Refuge in Alaska to oil drilling are dropped. The provisions, which include opening the East and West coasts and portions of the Florida Gulf Coast, as well as ANWR, to drilling, are supposed to help pay for transportation programs. But the Congressional Budget Office estimates they would raise less than $5 million over 10 years for the federal government.

"Opening ANWR to drilling as a means to pay for the transportation bill is neither reasonable nor realistic," said Rep. Charles Bass, R-N.H., author of the letter.

The bill also eliminates locally popular federal programs that help underwrite bike paths, bike lanes and pedestrian safety projects, including the Safe Routes to School program, in order to concentrate funding on highways.

"The House bill takes us back to the dark ages," Transportation Secretary Ray LaHood, a former Republican congressman, told reporters Monday. He said he doesn't expect any Democrats to vote for the bill.

"I hope there will be lots of opportunities to amend it," LaHood said, to increase funding for transit and other needs. "Without amendments, this bill isn't going to pass."

But Rep. John Mica, R-Fla., chairman of the House Transportation and Infrastructure Committee and co-author of a major portion of the bill, said he is "fairly confident" based on his discussions with GOP lawmakers that the bill can pass.

"This is going to be the No. 1 job creator and economic generator bill of this entire session (of Congress)," he said. "I think members will rally behind what may be their last chance of getting jobs and a responsible blueprint for dealing with our crumbling infrastructure."

There will be changes made to the bill through a leadership-backed amendment that will address GOP members' concerns, Mica said.

"The bill isn't done," he said. "The final bill will be something conservatives can be very proud of because it has dramatic reforms and measures that people have called for for years."

But House leaders are being squeezed from both sides. If they give too much ground they risk losing support on the right. The Club for Growth, a free-market, anti-tax group influential with fiscal conservatives, has told lawmakers it opposes both the House and Senate bills because they spend too much money. The political arm of the conservative Heritage Foundation has objected to the way the Senate bill is paid for. Democrats and moderate Republicans, meanwhile, oppose sharp cuts to popular programs.

Floor debate could begin on the House bill as soon as Wednesday, with a final vote expected Friday. Lawmakers had filed 293 amendment requests with the House Rules Committee by Monday's 11 a.m. deadline. The committee decides which amendments can be offered during debate.

Debate began on the Senate bill late last week with a strongly bipartisan procedural vote of 85-11, and is continuing this week. The bill is co-authored by Sens. Barbara Boxer, D-Calif., and James Inhofe, R-Okla., ideological opposites who have managed to overcome substantial disagreement in an effort to pass a bill.

But Democrats, who control the Senate, have struggled to come up with the money to pay for the plan. Several GOP senators have signaled that their support for the bill could turn to opposition if changes aren't made to satisfy their fiscal concerns.

Like the House, the Senate has been hampered by a shortfall between current spending levels and fuel tax revenues, which are the main source of funding for transportation programs. Reductions in driving due to the economy as well as more fuel-efficient vehicles have lowered tax revenues. The budget office projects the trust fund that pays for highway and transit programs will go broke sometime in the 2013 federal budget year.

Without an infusion of cash from somewhere, the Transportation Department could be forced to slow down reimbursements to states for highway construction and other transportation projects. That, in turn, could lead to thousands of lost jobs.

Lawmakers could resolve much of their money woes by increasing the 18.4 cent-a-gallon gas tax and the 24.4 cent-a-gallon diesel tax, but that's politically unpalatable in an economy where unemployment remains high and many Americans feel financially insecure.

Indecision about how to shore up the Highway Trust Fund has long stymied efforts to pass a transportation plan. The last long-term plan expired in 2009. Congress has kept programs going through a series of eight short-term extensions. The current extension expires March 31.