Lawmakers involved in the talks said they expected to present their report late Wednesday or early Thursday, with a House vote on Thursday.
The bill would provide $286.4 billion in the 2004-2009 period, replacing the $218 billion six-year program that expired in September 2003.
Passage has been a priority of this session of Congress and the last. But lawmakers have failed to resolve disputes with the White House over spending levels and with states over the distribution of federal highway money.
"Given the inadequate top line, it's a pretty decent bill," said Oregon Rep. Peter DeFazio, the top Democrat on the House Transportation and Infrastructure subcommittee on highways. He was one of many lawmakers who had sought significantly higher spending.
Congress has passed 10 temporary extensions of the old law. That has kept existing highway programs running but preventing the new ones from getting started — work that would create tens of thousands of jobs and address the serious infrastructure problems.
Stephen Sandherr, chief executive officer of the Associated General Contractors of America, said that considering the budgetary restraints and the war in Iraq, "I think we've squeezed every penny we could" from the negotiations.
He said a lot of states have been contracting for little besides maintenance work because of the uncertainty over when Congress would pass a new bill.
The agreement finalized Wednesday would create a formula where, toward the end of the program, each state would be guaranteed at least 92 cents in federal grants for every dollar contributed to the Highway Trust Fund through gasoline taxes. Under current law, states are assured a 90.5 percent return on contributions.
The final bill also would include specific projects requested by lawmakers for their districts or states. Such projects are often criticized by watchdog groups as political "pork." The two sides agreed that the Senate will choose 40 percent of the total.
These range from multimillion-dollar highways and bridges to bike paths, pedestrian trails and museum parking lots.
Several of the chief negotiators were quick to note what they had accomplished for their constituents. Sen. Kit Bond, R-Mo., said he had secured $50 million for Kansas City's Paseo Bridge, while Sen. Max Baucus, D-Mont., listed the "earmarks," or specific projects, he had gained, including $50 million for Going-to-the-Sun Road in Glacier National Park.
Slightly more than 18 percent of the funds would go to public transit, for bus and train projects and special programs for the disabled or to promote public transportation in national parks.
About $6 billion is directed to safety programs.
In the last session of Congress, the House committee sought as much as $375 billion for the bill, citing the importance of fixing deteriorating highways and bridges that are blamed for thousands of fatal traffic accidents every year.
But with the federal budget deficit reaching record levels, the White House insisted on a far lower level, and threatened that the president would veto any bill that added to the deficit or increased taxes.