The Federal Maritime Commission, in a move that threatens dockworker negotiations on East and Gulf Coast ports, asked a federal court yesterday to block a controversial work rule that returns jurisdictional control over cargo containers to the International Longshoremen's Association.

The rule, which gives the ILA the exclusive right to pack shipping containers within 50 miles of East and Gulf coast ports, has already been agreed to in a new national master agreement between the shippers and the union. The agreement does not go into effect, however, until the two sides complete negotiations for local contracts that expire Sept. 30.

Local negotiations were immediately suspended yesterday after the FMC and the U.S. Attorney's office for the Southern District of New York asked for the injunction against 121 domestic and foreign ocean shippers. A hearing on the request for an injunction is scheduled for Sept. 19.

The rule requires that containers packed within 50 miles of the ports be packed by ILA members. If they are not, the rule requires that ILA members unpack and repack the containers at dockside. The federal government seeks to bar the rule until FMC determines if it is legal.

"If the commission were seeking to willfully torpedo labor-management negotiations in the port industry, its timing could not have been better and its destructive action could not have been more on the mark," James J. Dickman, president of the New York Shipping Association said.

ILA President Teddy Gleason also denounced the move, calling it totally irresponsible.

In papers filed with the court, the FMC included 23 affidavits from various shippers and freight consolidators claiming that they have been damaged by the 50-mile rule. The FMC said it was taking the action to minimize the harm to these parties while the agency completes its inquiry into the legality of the rules.

The FMC is investigating whether the rules violate the 1916 Shipping Act by discriminating against one class of shipper. Hearings have been completed but a determination is not expected for several months.

The rule was first adopted in the early 1970s and has been the target of repeated attempts to get rid of it.

Earlier this year, the 50-mile rule was reinstated after Chief Justice Warren Burger denied a request for a stay that cleared the way for a National Labor Relations Board ruling. The NLRB found in February that the rule was legal and could go back into effect. An organization of freight consolidators is appealing the NLRB ruling to the federal appeals court in Richmond.

A subsequent move to strip the FMC of jurisdiction over the issue through federal legislation failed.

A union spokesman said it was too early to tell whether the FMC action might lead to a strike. The union's executive board will meet Sept. 20.

"A unanimous FMC is asking the court to stop the implementation of the 50-mile rules for very practical reasons," said FMC Chairman Alan Green Jr. "We have sworn statements from numerous shippers and consolidators that say they are being severely harmed by the rules' implementation.

"Even if the practice is ultimately found by the commission to be unlawful, it would be of little comfort to those elements of the maritime community which could suffer irreparable injury in the meantime," he said.