WASHINGTON (AP) — House and Senate leaders are making a last-ditch effort to revive stalled legislation to overhaul federal transportation programs — Congress' best bet for passage of a major jobs bill this year — but prospects for passage before the November election are dimming.

Senate Majority Leader Harry Reid, D-Nev., and House Speaker John Boehner, R-Ohio, as well as two key committee chairmen, Sen. Barbara Boxer, D-Calif., and Rep. John Mica, R-Fla., are scheduled to meet Tuesday to try to reach an agreement on how to handle a collection of sensitive policy and financing matters still in dispute.

A 47-member House-Senate committee has been holding negotiations on the bill for over a month, but they have been unable to reach agreement on a host of difficult issues, lawmakers involved in the process and their staffs said.

Time is running extremely short. Authority to spend money from the Highway Trust Fund — the main source of federal transportation aid to states — expires June 30. As a practical matter, congressional leaders need to make a decision by about Wednesday on whether to continue to try to pass a comprehensive bill, or whether seek a temporary extension of transportation programs. There are only about a half dozen days left in the month in which Congress is scheduled to be in session, and it takes time to prepare an extension bill and pass it.

Boehner has already signaled that if there is to be an extension, it should be at least six months long. That would push off the question of how to shore up the trust fund — which is forecast to go broke sometime next year — until after the election. Highway and transit programs have limped along under a series of nine extensions since the last long-term transportation bill expired in 2009.

The Senate passed a bipartisan, $109 billion transportation bill earlier this year that would consolidate current programs, give states more flexibility on how they spend federal aid and streamline environmental regulations to speed up completion of highway projects. House Republicans also crafted a comprehensive bill, but were unable to pass the measure. There are deep divisions within the GOP about whether transportation programs should be forced to live entirely with the revenue generated by federal gas taxes and other user fees, even if it means cutting programs by more than a third.

After several tries, House leaders gave up trying to pass their bill, and instead passed what was effectively a shell bill designed to meet legislative requirements necessary to begin negotiations with the Senate.

Senate Democrats have blamed intransigence by House Republicans for the stalemate in negotiations. Reid has suggested that House Majority Leader Eric Cantor, R-Va., is trying to delay the transportation bill in order to sabotage the economy.

Road-building and other industries dependent on highway programs have also identified House Republicans as the main obstacle to passage of a bill. A coalition of industry groups launched radio ads last week in the congressional districts of four House negotiators. "With billions of dollars at stake, and thousands of good paying jobs, it is time for Congress to take action," the ads said. "Will your congressman be part of the problem, or part of the transportation solution?"

GOP lawmakers have been working hard on the transportation bill, but they are insisting on reforms to prevent money from being misspent that Senate Democrats have so far resisted, Boehner told reporters Tuesday morning.

"I'm going to stress to Senator Reid and Senator Boxer that we want a bill," Boehner said, "but we are also going to insist on reforms of the process by which we spend the highway tax dollars that American motorists give us to rebuild America's highways."

The U.S. Chamber of Commerce sent a letter to lawmakers Monday urging them not to give up on a comprehensive bill. To do so would mean "the economic growth potential of infrastructure investment would be squandered and job losses would likely continue in the coming months and years," wrote Bruce Josten, the chamber's executive vice president.