Dakar, Senegal ? Any U.S. peacekeeping force sent to Liberia would face a volatile mix of combatants — from drunken government soldiers paid by the perks of looting and raping to angel-eyed child rebels toting AK-47s.

The United States has not sent a peace mission to Africa since its 1993 nightmare in Somalia. But despite the dangers, ventures by the British in Africa and by others elsewhere have shown how such efforts can work.

Three U.S. warships were bound Saturday for Liberia, carrying troops ordered up by President Bush to support a pending West African peacekeeping mission.

The deployment came as more deadly shelling hit Liberia’s refugee-crowded capital Monrovia, the target of a weeklong offensive by rebels trying to oust President Charles Taylor, a Boston-educated, Libyan-trained warlord. The downtown is the last stronghold of Taylor’s government.

A mortar shell slammed through the roof of a church sheltering thousands of refugees near the rebel-held port Saturday, killing at least three refugees and wounding about 55.

“Every day they’re talking, ‘Troops will come, troops will come,”‘ Konah Macgee, whose uncle was among those killed at the Great Refuge Temple, said of the promised multinational peacekeepers. “And no one comes.”

Bush has stopped short of saying American forces would participate directly in the mission to a nation founded in 1849 by freed American slaves.

For American troops, some dangers and difficulties are clear.

For one, the Geneva Conventions hold very little sway in Liberia. Fourteen years of near-perpetual conflict under Taylor have raised warfare among Liberians to the height of viciousness.

Each side is accustomed to executing captured enemies. Taylor’s side, in particular, is accused of often torturing them first.

Routinely, combatants in Liberia hack off slain rivals’ body parts as magic totems or simply to terrify.

The might of American Marines is widely respected here, making it less likely that warring sides would mete out similar treatment to any captured Americans. The strategic impact of an atrocity would be slight — but the damage to public opinion in the United States likely would be massive.

Since the Somalia mission in 1993, the image of a dead, naked U.S. soldier being dragged through the streets of Mogadishu almost on its own has kept American troops out of African peace missions. The soldier was one of 18 killed during an October 1993 raid.

Another, larger difficulty: Few fighters in Liberia show much interest in keeping their word.

Taylor repeatedly has made and broken peace pledges since launching Liberia into war in 1989. Most recently, he has hedged on promises to step down — something Bush has called for as a condition for sending troops. Taylor made another such pledge Saturday.

“Let nobody have any concern about, ‘Will President Taylor step down?”‘ Taylor told a prayer rally in Monrovia’s leading sports stadium. “I will step down.”