Panamanian forces, faced with a show of force by American troops, returned a shipment of U.S. military equipment that had been seized, the State Department said Friday.

The Panamanian Defense Force troops seized a shipment of supplies meant for SOUTHCOM, the U.S. military command in Panama, officials said. The equipment included a gun barrel for an M-1 Abrams tank.Sondra McCarty, a State Department spokeswoman, said Friday that the materiel, including the gun barrel, was returned "after a forceful U.S. response" to the confiscation.

She said the response included the movement of some U.S. troops to the Atlantic side of their military bases and "a heightened alert status of certain military units."

The PDF recognized that it had violated the Panama Canal treaty by seizing the materiel and that the U.S. shipments of military equipment "were clearly authorized," she said.

Earlier, State Department spokeswoman Phyllis Oakley said, "Nothing in the Canal treaty or related agreements prevents the United States from receiving shipments of military supplies or equipment through this port."

The State Department did not say how many U.S. troops were moved nor how much the U.S. military alert status was raised.

The Pentagon said that it had no immediate comment, but officials were working on a statement.

The U.S. protest was raised Friday at the Joint Military Committee, in an emergency meeting with Panamanian military officials.

The incident brought tensions to a new and higher level in a war of political and economic pressure between the two governments. Panama's president, Manual Solis Palma used the United Nations General Assembly this week to accuse the United States of waging a war of economic aggression and disinformation against his government.

McCarty said, "The Panamanian Defense Forces apologized for breaking the seals on the shipment and returned the gun tube."

The State Department has refused to deal directly with the Panamanian government dominated by Gen. Manuel Antonio Noriega and continues to recognize the former president, Eric Arturo Delvalle, who has remained in hiding somewhere in Panama.

Solis Palma, in his address to the U.N. General Assembly, said that the United States had reduced Panama's national income by 20 percent in the last year by withholding payments on canal tolls and other accounts.

Noriega, indicted on charges of drug trafficking by two Florida grand juries in February, rejected a U.S. deal to step down in return for the dropping of the indictments in May.

The seizure was disclosed Thursday by Lt. Col. Aquilino Siero, Panama's chief delegate to the combined Canal Defense Board, who said that a routine customs inspection of a U.S.-flagged cargo ship revealed a gun tube and other combat materials.