By THOM SHANKER
 
WASHINGTON, Feb. 22 - State Department and Pentagon officials are expressing renewed concern that Nicaragua may not destroy its arsenal of portable antiaircraft missiles as it promised Defense Secretary Donald H. Rumsfeld during his visit to Managua last autumn, administration officials said Tuesday.

An American delegation was in Managua on Tuesday to renew pressure on the Nicaraguan government to destroy all of the shoulder-fired missiles supplied by the Soviet Union and Cuba during the 1980's. The American group was led by Rose Likins, the acting assistant secretary of state for political-military affairs.

A range of United States government and intelligence officials have said the shoulder-launched missiles are highly sought by terrorists and criminal groups, who might use them to shoot down a commercial airliner, a military passenger plane or a helicopter ferrying government and military personnel. The missiles are suitcase-sized and can be easily smuggled.

"We do have a team down there of State Department and Pentagon officials working on the issue," Richard A. Boucher, the State Department spokesman, said Tuesday at a news briefing. "This has been a longstanding issue, one that we have worked productively with the Nicaraguan government on."

Mr. Boucher said President Enrique Bolaños of Nicaragua had given assurances several times "that Nicaragua would destroy all of its man-portable missiles in order to reduce the chance that they might fall into the hands of criminals and terrorists."

The most recent high-level discussion took place last November, when Mr. Rumsfeld received an unambiguous pledge from President Bolaños that Nicaragua would destroy the entire stockpile of missiles.

But two recent events prompted the current American delegation's visit, officials said. One was a recent sting operation in Nicaragua in which a Soviet-made SA-7 missile was purchased on the black market by an undercover team of Nicaraguan and United States law enforcement officers.

The other was a vote by the National Assembly, dominated by opponents of Mr. Bolaños, which last week stripped the president of authority to dispose of military weapons and required that he seek its approval for any further destruction of missiles.

"I think we've been satisfied with some of the efforts the Nicaraguan government has made to destroy missiles, to the sting operation that helped identify that there might be others out there," Mr. Boucher said. "But, obviously, the National Assembly vote creates difficulties, and it's one of the reasons why we want to get a team down there to try to work with them to help make sure the government can fulfill the pledge that it made at very high levels."

A spokesman for the Nicaraguan Embassy in Washington declined to comment, saying all official statements would have to come from the government in Managua after the visit.

The United States demonstrated its unhappiness this week over the pace at which Nicaragua is destroying the missiles by sending a major, instead of the higher-ranking officer that protocol might have dictated, to the promotion ceremony on Monday for Gen. Omar Hallesleven of the Nicaraguan Army, a senior Pentagon official said.

Between 1,000 and 1,400 of the SA-7 missiles remain in the Nicaraguan arsenal, according to Pentagon officials.

Last year American intelligence agencies tripled the formal estimate of the number of shoulder-fired missile systems believed to be at large worldwide, since determining that at least 4,000 of the weapons in Iraq's prewar arsenals could not be accounted for.

In 2002 attackers who fired two SA-7's almost hit a commercial aircraft taking off from Mombasa, Kenya.