A private bodyguard hired by Sen. Edward M. Kennedy (D-Mass.) to protect him on his current South American trip was arrested last week, hours before flight time, when he entered a Senate office building carrying two submachine guns, a pistol and 146 rounds of ammunition in six clips.

"We're talking a small army," explained one source familiar with the arrest.

Kennedy called Attorney General Edwin Meese III shortly after the arrest in an apparent attempt to have the bodyguard released and to retrieve the weapons, according to a Justice Department source. The call was initially returned by the U.S. attorney's office.

"The senator's primary concern was leaving the city with adequate protection for himself and his sisters Jean Smith and Pat Lawford , who are traveling with him," said Bob Mann, Kennedy's spokesman. "This office made every effort to do that."

After a flurry of high-level negotiations, according to Mann, Treasury Secretary James Baker authorized Secret Service protection for the senator for the first leg of his trip to Brazil, Argentina, Peru and Uruguay. A Secret Service spokesman said last night that the agency was reimbursed by the senator's office for costs incurred.

The bodyguard, Chuck Stein -- who has been employed by Kennedy on a number of occasions when the senator has traveled abroad -- was released on his own recognizance following an arraignment. He was released in time to make the late-afternoon flight Jan. 7 with Kennedy. Stein has been ordered to reappear in court Jan. 28.

He could not be reached for comment yesterday, as he was traveling from Argentina to Peru.

Stein, who is based in California, had just arrived in Washington on the afternoon of Jan. 7 and was attempting to join Kennedy at the Russell Senate Office Building en route to the airport. He stopped at the guard's desk and asked where he might leave his weapons. A Capitol Hill policeman promptly placed him under arrest.

According to sources close to the incident, the arrest triggered an avalanche of phone calls from Kennedy and his staff to officials throughout the city. D.C. Police Chief Maurice Turner, contacted by the U.S. attorney's office, confirmed that D.C. law required that the weapons be held as evidence and eventually destroyed.

Stein, meanwhile, was detained and charged with one count of carrying a pistol without a license, two counts of possession of unregistered firearms and one count of possession of unregistered ammunition. In addition to the pistol, Stein was carrying two semiautomatic weapons, an Israeli-made Uzi and an Italian-made Beretta.

It was not known why Stein did not simply keep the guns in the car.

"You'll have to ask Chuck that," said Mann. "This was an unfortunate incident that occurred with very good intentions on the part of Mr. Stein and the part of the police. He was just trying to be up front by telling the guard about the guns."

Stein is licensed to carry the weapons in California but not in the District.

Mann said Stein may have carried weapons in Washington on other occasions. "We really can't be sure why it never happened before," he said. "Maybe they were together as they moved about. He was alone this time and he assumed he was doing the appropriate thing, but because of this technical glitch in the law, he was stopped."

Mann added that "this office is in strict support of gun control laws and we take no issue with everyone following legal procedures . . ."

With help from the State Department, Kennedy's office obtained permission for Stein, whose guns remain with police here, to use government weaponry for the last part of the South American trip. According to Mann, the Secret Service agent left Kennedy after two days, and Stein is being provided with two semiautomatic weapons by the U.S. embassies in each of the countries Kennedy is visiting. In each country, Mann said, Stein is given the weapons upon arrival and returns them upon departure.

Kennedy left Jan. 7 for a 12-day South American trip to discuss the Latin American debt crisis with the presidents of Brazil, Uruguay and Argentina. According to Mann, he is traveling with his sisters in celebration of the 25th anniversary of John F. Kennedy's Alliance for Progress.