OAKLAND  (AP) — Custodial and maintenance workers picketed Tuesday at one of the nation's busiest ports, blocking trucks from picking up and delivering goods on what had been expected to be a busy day before the holidays.

Ships waited at six of the seven terminals at the Port of Oakland, as intermittent rain soaked hundreds of angry workers who carried signs and blocked entrances during the one-day protest over stalled contract talks.

Passing motorists blared horns and supporters pounded drums as strikers chanted, "Shut it down, we're a union town!"

"We're letting management and the public know that they can't treat us like that," said Lynn Riordan, a communications staffer for Service Employees International Union Local 1021.

Across town, dozens of additional service union members picketed at Oakland International Airport after walking off their jobs late Monday. Those employees are covered under the same contract as port workers.

No flights were affected, port spokesman Isaac Kos-Read said.

The port declared an impasse in negotiations in May, and the two sides were scheduled to meet on Nov. 29. The talks broke down amid issues involving pay, benefits and a demand by the port that custodial and maintenance workers contribute to their retirement fund.

Numerous dockworkers, who load and unload cargo vessels, refused to cross the picket line at the port as a show of solidarity with the protesting workers.

"These service workers have effectively shut down the port," said Jack Heyman, a retired longshoreman from Oakland who chairs the International Longshore and Warehouse Union's transport workers solidarity committee.

Dozens of truck drivers decided not to interrupt the protest.

"What can you do?" David Soria, a driver for Modesto-based Rocha Transportation, said as he waited to drop off a shipment of wine. "My company told me to stay, so I'll stay. And wait."

Kos-Read said it was unfortunate that truckers were forced to stop work and wait in the rain.

The port handles roughly about 2.3 million cargo containers a year, generating about $300 million in revenue. Officials, however, say the facility is $1.3 billion in debt.

The service union, which represents electricians, clerical workers, security personnel and janitors, claimed the port is withholding requested financial information. The union also said port officials have implemented unilateral changes during bargaining sessions.

"We're showing you that if you don't take us seriously, we have the ability to shut down the port," said Gary Jimenez, a union vice president.

The protest marked the latest work stoppage at the port within the past 12 months. Occupy Oakland demonstrators shut it down twice last year.