Backed by thousands of chanting supporters Tuesday, the Somali capital's largest clan threatened to attack Islamic militiamen who do not leave part of the city they seized this week in a blow to U.S. foreign policy.

Protesters shouted "We don't need Islamic deception!" and "We don't want Islamic courts, we want peace!" at a rally called by the Abgal clan. The leaders of the capital's largest and historically strongest clan had controlled northern Mogadishu since 1991.

CountryWatch: Somalia

Islamic militiamen maintained positions about a mile from the protest but did not move to stop it.

The Islamic Courts Union militia on Monday drove out the fighters of a secular alliance backed by the United States, which fears that the nation of 8 million could fall under the sway of Al Qaeda.

The militia became the first group to consolidate control of Mogadishu since this impoverished Horn of Africa nation descended into anarchy 15 years ago.

But Tuesday's protest showed that the Islamic militia may have to negotiate with clan leaders to keep control of the capital.

"If the so-called Islamic courts don't stop invading our territories ... the country will return to civil war," said Sheik Ahmed Kadare, an Abgal elder. The clan did not give a timetable for a potential attack.

Tuesday's rally appeared to be an attempt to redefine the conflict in the capital as a competition between clans, rather than a religious battle, in order to build support for continued fighting if the Islamic militants do not retreat.

The Abgal clan leaders promised to set up new, clan-based courts in northern Mogadishu to replace those that the Islamic extremists have operated in recent years in order to raise money and goodwill for their bid to take over the country.

The courts have said a government based on Islamic law will restore order to Somalia.

U.S. officials said recently that Islamic leaders in Mogadishu are sheltering three Al Qaeda leaders indicted in the 1998 U.S. Embassy bombings in Kenya and Tanzania. The same Al Qaeda cell is believed responsible for the 2002 suicide bombing of an Israeli-owned hotel in Kenya, which killed 15 people, and a simultaneous attempt to shoot down an Israeli airliner over Kenya.

The U.S. officials, speaking on condition of anonymity because of the sensitivity of the issue, have confirmed cooperating with the secular warlords defeated by the miltiamen Monday.

The president of Somalia's transitional national government also has said Washington is funding the secular alliance. The Bush administration has not confirmed or denied that, saying only that it supports those who fight terrorism.

Secular alliance leaders were on the run after Monday's capture of Mogadishu; at least two of them — Bashir Rageh and Muse Sudi Yalahow — have pledged their loyalty to their Abgal clan.

"Our clan has agreed to defend our land and we will fight the courts hiding under the cloak of Islam and trying to fool our people," said Rageh, who arrived at the demonstration with Yalahow, escorted by Abgal militiamen.

The battle between the militia and the secular alliance had been intensifying in recent months, with more than 300 people killed and 1,700 wounded — many of them civilians caught in the crossfire of grenades, machine guns and mortars.

The Islamic militants and their secular rivals began competing for influence in earnest after a U.N.-backed interim government slowly began to gain international recognition.

But the weak government, wracked by infighting, has not even been able to enter the capital because of the violence. Instead, it is operating out of a base in Baidoa, 155 miles from Mogadishu.

Weapons prices soared there Monday amid fears the militia could head to Baidoa next.

The United States has not carried out any direct action in Somalia since the deaths of 18 servicemen in a 1993 battle in Mogadishu depicted in the film "Black Hawk Down."