LOS ANGELES — Thousands of West Coast dockworkers kept working yesterday without a contract after negotiators failed to reach an agreement on a new labor pact.

The workers agreed to stay on the job while negotiations continue, said Craig Merrilees, a spokesman for the International Longshore and Warehouse Union.

"There's really no choice but to keep working and to get it done," he said.

The previous six-year contract with shipping companies expired at 5 p.m. Tuesday.

The decision by dockworkers is a break for the troubled U.S. economy, since the billions of dollars in cargo handled by 29 West Coast ports represents about 11 percent of the U.S. gross domestic product.

Steve Getzug, a spokesman for the Pacific Maritime Association, which represents 71 shipping companies and terminal operators, said the organization is committed to reaching a fair deal and keeping West Coast ports running.

Contract talks began in March. About 26,000 workers are affected at ports in California, Oregon and Washington.

Negotiations were held over the weekend and into the late hours Monday before resuming Tuesday in an eleventh-hour effort to reach an agreement.

Combined, the ports moved 12.2 million cargo containers last year and accounted for an annual domestic economic impact of $1.2 trillion, according to the association.

The twin ports of Los Angeles and Long Beach handle about 40 percent of the nation's cargo.

Both sides are hoping to avoid a repeat of a bitter labor dispute that led to a 10-day lockout in 2002 and an estimated $15 billion in economic losses.

The union and the shippers previously disclosed they had reached a tentative agreement on healthcare benefits. Wage, pension, safety and productivity issues remained under discussion.

Shippers have said the average full-time dockworker made $136,000 in 2007, placing them among the best paid blue-collar workers in the nation.

The union disputes that figure, stressing that only about 10,000 of the 25,000 workers covered by the current contract work full-time or more hours.

"The pay is important but other issues are also real, real important," Merrilees said. "Folks want to make sure that a number of issues are addressed."