ASSOCIATED PRESS WRITER

PAUL ALEXANDER

MOGADISHU, Somalia (AP)—The Somali security chief for the CARE aid agency was killed Monday when U.N. peacekeepers fired on gunmen who attacked them in territory controlled by Mohamed Farrah Aidid.

The attack was the fourth on foreign troops in as many days and suggested that Aidid’s monthlong truce with U.N. forces seemed to be crumbling.

Meanwhile, a showdown with the United States loomed.

A spokesman for the U.S. force in Somalia criticized Aidid as being ‘‘uncooperative’‘ and said the United States was sticking by plans to put American forces back on Mogadishu’s streets.

Aidid, whose followers control southern Mogadishu, had been clashing with the United Nations since June, when the United Nations blamed him for the deaths of 24 Pakistani peacekeepers. But after four months of fierce battles with U.N. forces, he declared a truce Oct. 9.

Some people have speculated that Aidid was trying to buy time until the United States withdraws from Somalia in March.

But Aidid, who has gotten no tangible rewards for releasing an American pilot and a Nigerian peacekeeper last month, has been known to strike back when his power seems to be waning. And at a news conference Sunday, he made it clear that the old acrimony toward the multinational mission had not dissipated.

He vowed not to negotiate with the United Nations, and on Monday, his Somali National Alliance boycotted two U.N.-sponsored meetings: one to discuss how to improve the city’s security, the other to meet face-to-face with the faction headed by Ali Mahdi Mohamed, which controls Mogadishu’s northern half.

‘‘The United States has been bending over backwards to meet some of the requests’‘ by the Somalia National Alliance, U.S. military spokesman Col. Steve Rausch said Monday. ‘‘We are disappointed. They seem uncooperative.’‘

He did not specify what requests Aidid’s faction made.

At his news conference Sunday, Aidid said there could be trouble if U.S. troops return to the streets after a six-month hiatus. On Monday, confrontation edged closer when Rausch reaffirmed that Army reinforcements soon will be venturing beyond their compounds.

‘‘You will see an increased presence,’‘ he said, adding a warning of his own about the repercussions of Americans coming under fire: ‘‘These forces are very capable. They are very lethal.’‘

Even so, the United States, wary about being perceived as provocative and hoping to keep the cease-fire alive, has pushed back the starting date for joint checkpoints and patrols with forces from other countries. When the Americans moved into their new base outside the capital a week ago, officials talked about a couple of days. Now they say a couple of weeks.

Americans have been off Mogadishu’s streets since May, when the United States handed over command of the multinational mission to the United Nations. But although Americans will resume patrols, Rausch said there will be no active program to disarm Somalis, despite concern that the number of weapons on the street threatens the quiet in Mogadishu.

In the Somali capital, quiet is a relative thing. The last pitched battles occurred more than a week ago, but gunmen tote assault rifles while strolling the streets or clinging to the top of the crowded pickup trucks. No one flinches at the sound of distant gunshots.

Since Friday, gunmen have been taking potshots at U.N. troops, injuring several Somalis but no peacekeepers.

The increased violence rolled right up to the United Nations’ door Monday. Turkish guards fired warning shots to force off Somalis angered when told no jobs were available at the U.N. compound.

Two hours later, two gunmen opened fire on a convoy of Malaysian armored personnel carriers, which shot back, said U.N. military spokesman Capt. Tim McDavitt.

Simon Israel of CARE confirmed that the Malaysian troops came under fire, but said they shot back indiscriminately, killing CARE’s Somali security chief. CARE has filed a complaint with the United Nations and is seeking compensation for the Somali worker, who leaves a widow and eight children.