Facing unprecedented congestion at the ports of Los Angeles and Long Beach, the Harbor Trucking Association announced Thursday that it will seek an exemption from a federal mandate that regulates when truck drivers can work.

The association will petition the Federal Motor Carrier Safety Administration for an exemption to a provision requiring a 34-hour rest period for truckers, which would allow one of the largest marine terminal operators on the waterfront, Long Beach Container Terminal (LBCT), to open its gates on Sundays to move backed-up cargo.

“Something has to be done,” said LBCT President Anthony Otto, whose terminal already is open Friday nights to improve goods flow. “We need to move freight.”

Under the federal mandate, truck drivers are allowed to work 70 hours within an eight-day period. They also must have two 1-5 a.m. off-duty periods during 34 consecutive hours of rest. Most drivers take that time off on Fridays and Saturdays, making it difficult for drivers to work on Sundays.

“The same story I get from everyone is, ‘I’d love to come on Sunday, but I’ve run out of hours,’ ” Otto said.

The exemption would give drivers more flexibility in their work schedule, said Alex Cherin, executive director of the Harbor Trucking Association, adding that the so-called restart provision applies more to long-haul truckers.

The petition process is expected to take 60 to 90 days.

Otto has proposed opening his terminal’s gates on Sundays once the petition is granted if there are enough trucks to justify being open.

The association’s petition and LBCT’s proposal to open on Sundays are the latest in a multipronged effort by the supply chain to move cargo clogged up within the nation’s two busiest seaports.

Customers have been complaining about delays in the delivery of goods due mostly to unresolved labor talks, the lack of available chassis, or trailers, to carry cargo, and the arrival of bigger vessels delivering larger quantities of goods.

The ports of Los Angeles and Long Beach have been in talks with stakeholders on how to resolve the chassis issue, which created congestion after carriers shifted the responsibility of providing chassis to a different operator, resulting in a critical shortage.

In a four-hour meeting with stakeholders last week, the Port of Los Angeles brought together three major chassis providers and a terminal operator — all of whom have the majority of chassis, more than 95,000 — and persuaded them to create a pool system to share them.

The providers — Direct ChassisLink Inc., TRAC Intermodal, Flexi-Van and SSA Terminal — are expected to roll out the chassis pool by Feb. 1. This week, they are hammering out the logistics of that rollout, including the selection of a third-party provider that could independently facilitate the process.

“There’s a lot of work to do in this area, but I’m encouraged that for the first time these three guys, plus SSA folks, were able to sit down and talk about this idea,” Port of Los Angeles Executive Director Gene Seroka said Thursday. “This is a significant step forward.”

Meanwhile, Port of Long Beach Chief Jon Slangerup has proposed freeing up of more truck trailers by providing an area in the port where drivers could leave empty shipping containers for temporary storage while they retrieve loaded imports from Long Beach docks.

“We are taking measures to ease congestion by freeing up more chassis,” said Port of Long Beach Chief Commercial Officer Noel Hacegaba. “The solutions that are being put into action will ease and speed cargo flow during the peak season.”