Press TV reported that Hundreds of American protesters, angered by Israel's recent deadly assault on the Gaza Strip, gathered at the Port of Oakland to block an Israeli ship from unloading its cargo.
Workers with the International Longshore and Warehouse Union (ILWU) refused to unload the Zim Shanghai as about 200 activists picketed outside several of the port's gates on Saturday morning.
The cargo ship is managed by Israel's largest shipping firm, Zim Integrated Shipping Services.
About 50 police officers were also present at the port.
The protesters said they would continue with their "Block the Boat" campaign.
They said Israeli authorities must be held responsible for the deaths of more than 2,100 Palestinians during the recent 50-day war on Gaza.
"I think it was a big victory today for those who are opposed to the policies of Israel in Gaza," said Steve Zeltzer, an organizer of the protest.
Similar actions were taken in August, when protesters blocked Israeli-owned ship Zim Piraeus for five days, forcing it to leave for Los Angeles with most of its cargo unloaded.
Longshore workers refused to cross picket lines to unload Zim Piraeus in August.
Protesters on Saturday said they hoped to achieve the same outcome.
"We ask the ILWU to carry on its long historical tradition of opposing injustice and honoring community picket lines. Let's keep the pressure on and continue this tradition of labor blockades against oppression," the "stop ZIM action committee" said in a statement.