DETROIT (AP) -- With a strike deadline looming, the group representing East and Gulf Coast ports is asking a federal agency to make the Longshoremen's union come to the bargaining table to negotiate a new contract.

The U.S. Maritime Alliance says it filed an unfair labor practice charge with the National Labor Relations Board alleging that the International Longshoremen's Association is not bargaining in good faith.

The alliance said in a prepared statement Thursday that it filed the charge "due to the ILA's repeated refusal to come to the table and bargain on a new master contract."

The ports are asking for immediate relief, an order requiring the union to resume bargaining. It was unclear just how fast the NLRB might act on the request. A message was left seeking comment from the agency. Its unlikely that the NLRB will rule on the complaint before the Tuesday strike deadline, and with no talks scheduled, a strike appears to be likely.

The NLRB request comes just four days before the ILA's six-year contract with the ports expires, and the union representing 45,000 dockworkers from Maine to Texas says it will go on strike at 12:01 a.m. on Tuesday.

The two sides haven't bargained since June in a dispute largely over wages and a union-proposed ban on increased automation of port cranes, gates and trucks that could cost jobs.

A message also was left Thursday seeking comment from the union.

"USMX has been clear that we value the work of the ILA and have great respect for its members," the alliance statement said. "We have a shared history of working together and are committed to bargaining."

In early bargaining, industry analysts say the union sought 77% pay raises over six years to make up for inflation and give workers a chunk of the billions made by shipping companies since the coronavirus pandemic.

The union says both sides have communicated multiple times in recent weeks, but a stalemate remains because the Maritime Alliance is offering a pay increase that's unacceptable.

Top-scale port workers now earn a base pay of $39 an hour, or just over $81,000 a year. But with overtime and other benefits, some can make in excess of $200,000 annually. Neither the union nor the ports would discuss pay levels. But a 2019-2020 report by the Waterfront Commission, which oversees New York Harbor, said about a third of the longshoremen based there made $200,000 or more.

In a statement issued Monday, the ILA said it refutes claims it attributed to the alliance that the union's demands amount to a wage increase of over 75% over the life of the contract.

"Deceiving the public with misleading calculations is not going to help get an agreement with the ILA," President Harold Daggett said in the statement issued Monday.

The union has said shippers have made billions since the pandemic began. Copenhagen-based-Maersk, among the world's largest container shipping companies, made more than $50 billion in profits over the past four years. Earnings, though, dropped substantially in 2023 as pandemic-era consumer demand eased and brought sky-high freight rates back down.

A strike would shut down as many as 36 ports that handle nearly half of the cargo going in and out of the U.S. on ships.

If a strike were resolved within a few weeks, consumers probably wouldn't notice any major shortages of retail goods. Many retailers and other businesses have stocked up on goods in anticipation of a strike.

But a work stoppage that persists for more than a month would likely cause a shortage of some consumer products, although most holiday retail goods have already arrived from overseas.

A prolonged strike would almost certainly hurt the U.S. economy. Even a brief strike would cause disruptions. Heavier vehicular traffic would be likely at key points around the country as cargo was diverted to West Coast ports, where workers belong to a different union not involved in the strike. And once the longshoremen's union eventually returned to work, a ship backlog would likely result. For every day of a port strike, experts say it takes four to six days to clear it up.

If a strike occurs, it would be the first national work stoppage by the ILA since 1977.