NEWARK, N.J. - Container traffic at some ports was slowed Monday as a threatened strike by independent haulers began to take effect.

Protesting truckers succeeded in reducing truck traffic in and out of marine terminals at the Port Newark/Elizabeth container complex Monday.

Trucking companies and terminals said many owner-operators parked their rigs and refused to move containers, while organizers of the protest distributed leaflets. Trucks were still moving in and out of marine terminals, but operators said the flow was lighter than usual, especially for a Monday.

Tom Adamski, chief executive of Cross Port Transportation of South Kearny, N.J., and chairman of the Bi-State Harbor Carriers Conference of the New Jersey Motor Truck Association, said the work stoppage appeared to be "90 percent effective" among owner-operators, and that traffic in and out of terminals was dominated by over-the-road or company-owned vehicles.

Truckers earlier announced plans for a nationwide strike this week, the start of the peak shipping season, in a loosely coordinated effort to pressure shipping lines to pay higher diesel fuel surcharges.

The Teamsters union at the time denied that it was behind the calls for a strike, but urged steamship lines to compensate drivers for high fuel costs or face dockside protests.

The strike was also affecting shipments at Port Everglades and the Port of Miami.

There were no immediate reports of protests at other ports.

"They have a valid cause, but they're not going about it the right way," said Jeff Bader, association president and president of Golden Carriers. Bader said that instead of a general shutdown, drivers should direct their complaints to steamship lines that don't adequately compensate trucking companies for fuel and other costs.