The federal Highway Trust Fund will run out of cash this summer, marking the second year in a row that gasoline tax revenues have failed to meet prior projections and federal spending commitments.

Congress will need to add between $5 billion and $7 billion to keep the trust fund solvent for now, Sen. Barbara Boxer , D-Calif., announced Tuesday. Boxer chairs the Environment and Public Works Committee, which has jurisdiction over highway spending.

Boxer said White House officials told Democratic staffers last month that an additional $8 billion to $10 billion would be needed to finance projects already authorized through the end of fiscal 2010.

She announced the shortfall at a Tuesday committee hearing on President Obama’s nomination of Victor M. Mendez to head the Federal Highway Administration.

Congress approved an $8 billion transfer of general tax revenues in September to shore up the Highway Trust Fund, which ran low because revenues from gasoline and diesel fuel have slowed as motor vehicles become more fuel-efficient and Americans drive less because of the economic recession.

A permanent solution could come in the next surface transportation reauthorization bill, though the available financing options are contentious and it’s possible that a new bill will not be completed by the time the current law expires Sept. 30.

House Transportation and Infrastructure Committee Chairman James L. Oberstar , D-Minn., is expected to unveil his blueprint for the reauthorization June 9. Only 400 pages of the 800-page bill had been drafted before last week’s recess, a committee aide said.

Oberstar’s bill will focus on revamping federal programs and policy. The Ways and Means Committee has jurisdiction over the gas tax and other financing options.

Options for replenishing the trust fund include raising the 18.4-cent-per-gallon tax on gasoline, borrowing more from the general treasury or cutting highway and public transit spending significantly.