Union officials declined to discuss their objectives for a new contract.

Mr. McKenna, the maritime association chief executive, said the union had yet to outline demands while declining to engage in discussions before May.

He expected that the union would resist efforts to expand automation at the ports, a traditional point of contention. He said greater automation — such as adding self-driving vehicles and robotics to move cargo — was unavoidable in ports in dense urban places like Los Angeles. There, land is tight, so growth must come from increasing efficiency, rather than physically expanding.

The last time the I.L.W.U. contract expired, West Coast ports suffered months of debilitating disruptions — the source of enduring recriminations.

Terminal operators accused dockworkers of slowing operations to generate pressure for a deal. The union countered that employers were the ones creating problems.

Some dockworkers question whether terminal owners are sincerely seeking to speed up cargo handling, given that shipping rates have soared amid chaos at the ports.

Jaime Hipsher, 45, drives a so-called utility tractor rig — equipment used to move containers — at a pair of Southern California shipping terminals. One is operated by A.P. Moller-Maersk, a Danish conglomerate whose profits nearly tripled last year, reaching $24 billion.

She said maintenance of equipment was spotty, producing frequent breakdowns, while the terminals were often understaffed — two problems that could be fixed with more spending.

A Maersk spokesman, Tom Boyd, rejected that characterization.

“Freight rates have been impacted by the global Covid-19 recovery and the demand outpacing supply,” he said in an emailed statement. “Ships at anchor are not productive, nor are they earning revenue against a backdrop of large fixed costs.”

That Ms. Hipsher spends her nights on the docks represents an unexpected turn in her life.

Her father was a longshoreman. He urged her to attend college and do something that involved wearing business attire, in contrast to how he spent his working hours — climbing a skinny ladder to the top of ships and loading coal onto vessels.

“He would come home after work and he would have coal dust coming out of his ears, out of his nose,” Ms. Hipsher recalled. “His hands would just be completely black.”

But in 2004, when she was working as a hairstylist, her brother — also a longshoreman — suggested that she enter a lottery for the right to become a casual dockworker.

The ports had changed, her brother said. Growing numbers of women were employed.

Eighteen years later, Ms. Hipsher has gained the security of seniority, health benefits and a pension.

As contract talks approach, she pushes back against the notion that the union poses a threat to the global economy.

“You’re complaining about my wages, thinking that my wages are the source of inflation, and we don’t deserve it,” she said. “Well, look at the billions that the owners are making.”

Emily Steel contributed reporting.

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