NEW YORK — Ports from Maine to Texas shut down this week when the union representing about 45,000 dockworkers went on strike for the first time since 1977.

Workers began walking picket lines early Tuesday near ports all along the East and Gulf coasts.

A shutdown that lasts more than a few weeks has the potential to raise prices and create shortages of goods throughout the country as the holiday shopping season — along with a tight presidential election — approaches.

There have been some signs of movement in the talks, with the U.S. Maritime Alliance, which represents ports and shipping companies, saying both sides have moved from their initial wage offers. But Wednesday, the alliance called on the International Longshoremen’s Union to come to the bargaining table.

“We cannot agree to preconditions to return to bargaining, but we remain committed to bargaining in good faith,” the group said in a statement.

Late Wednesday, the ILA said that Harold Daggett, its president, and other union officers had received death threats since the strike began. The union said the threats were reported to police.

The union is demanding significantly higher wages and a total ban on the automation of cranes, gates and container-moving trucks used in the loading or unloading of freight at 36 U.S. ports. Those ports handle roughly half of the nations’ cargo from ships.

The contract between the ILA and the alliance expired Tuesday.

The union’s opening demand was a 77% pay raise over the six-year life of the contract, with Daggett saying that it would make up for inflation and years of small raises. ILA members make a base salary of about $81,000 per year, but some can pull in over $200,000 annually with large amounts of overtime.

On Monday, before workers hit the picket lines, the alliance said it had increased its offer to 50% raises over six years, and it pledged to keep limits on automation in place from the old contract. The alliance also said its offer tripled employer contributions to retirement plans and strengthened health care options.

If a strike were deemed a danger to U.S. economic health, Biden could, under the 1947 Taft-Hartley Act, seek a court order for an 80-day cooling-off period. This would suspend the strike.

But during an exchange with reporters Sunday, Biden said “no” when asked if he planned to intervene.

“Because it’s collective bargaining, I don’t believe in Taft-Hartley,” Biden said.

If the strike is resolved within a few weeks, consumers probably wouldn’t notice any significant shortages or price hikes. But a work stoppage that persists for more than a month could be a different story, depending on what you’re shopping for. Most holiday retail goods have already arrived from overseas, so there is a buffer. Prices on everything from fruits and vegetables to cars may head higher, at least temporarily, if it drags on.