OAKLAND, Calif. (AP) -- Anti-Wall Street protesters along the West Coast joined an effort Monday to blockade some of the nation's busiest docks, with the idea that if they cut off the ports, they cut into corporate profits.

The protesters are targeting the locations because they believe American ports have become "economic engines for the elite." They are most upset by two West Coast companies - giant West Coast port operator SSA Marine and grain exporter EGT - that they believe epitomize the big corporations that make up the "1 percent."

Goldman Sachs owns a major stake in SSA Marine, and the bank has been a repeated target of Occupy protesters since the movement began. The two port companies have also engaged in high-profile clashes with union workers lately, and the Occupy protesters want to stand up for the workers.

Several hundred people began picketing at the Port of Oakland before dawn and blocked some trucks from going inside. Police are monitoring at the scene, but no major clashes have been reported so far. Occupy protesters successfully shut down the port in November.

In Southern California, as many as 400 demonstrators gathered in a park and planned to march on the Port of Long Beach. Occupy protesters said they plan to head to a dock facility owned by SSA Marine.

About 300 people gathered at Kelly Point Park in Portland, Ore., and Kari Koch, organizer with Shut Down the Ports Working Group of Occupy Portland, said she expected hundreds more to picket the nearby terminal. Police arrested three people and seized a gun and sword from people who said they were on the way to the demonstration.

Occupy groups also planned blockades in Seattle, Tacoma, Wash., and Vancouver, British Columbia.

The protests being billed as action against "Wall Street on the waterfront" are perhaps the Occupy movement's most dramatic gesture since police raids sent most remaining camps scattering last month. Demonstrators began forming those camps around the country about two months ago to protest what they call corporate greed and economic inequality.

"We will not stand for corporate profits at the expense of working people, we will not stand for attacks on workers, and we will not allow our schools to be closed, social services slashed, and families to be impoverished by your greed!" Koch said Monday in statement.

The Port of Oakland has appealed to city residents not to join the blockade, which they said could hurt the port's standing among customers and cost local jobs.

"The port is going to do all that it can to keep operations going. Our businesses need to hear that. Our workers need to know that," said Port of Oakland spokesman Isaac Kos-Read.

Officials at West Coast ports said they have been coordinating with law enforcement agencies as they prepare for possible disruptions. Protesters said police violence against blockades in any city will trigger an extension of blockades in other cities as a show of resolve.

Organizers of the port demonstrations said they hope to draw thousands to stand in solidarity with longshoremen and port truckers they said are being exploited, though the International Longshore and Warehouse Union, which represents many thousands of longshoremen up and down the West Coast, has distanced itself from the shutdown effort.

The union's president suggested in a letter to members that protesters were attempting to co-opt the union's cause to advance their own agenda.

Protesters have cited a longstanding dispute between longshoremen at the Port of Longview in Washington and grain exporter EGT as a key reason for the blockades. Shutdown supporters said they're not asking longshoremen to organize a work stoppage in violation of their contract but simply asking them to exercise their free speech rights and stay off the job, in keeping with the union's historic tradition of activism.

If protesters muster large enough numbers to block port entrances, arbitrators could declare unsafe working conditions, which would allow port workers to stay home.

Organized labor appears divided over the port shutdown effort. In Oakland, which saw strong union support for the Nov. 2 general strike that culminated in the closing of the port, the city's teachers union is backing Monday's action, while the county's construction workers have come out against the shutdown, saying the port has provided jobs to many unemployed workers and apprentices.

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