NAIROBI, Kenya — A major offensive by Islamic rebels has brought Somalia’s internationally backed government close to collapse and renewed the possibility that a militant Islamist regime that allegedly has ties to al Qaeda could seize control of the East African nation.

That would be a devastating blow to U.S. counter-terrorism and anti-piracy efforts in East Africa, where al Qaeda operatives bombed the U.S. embassies in Kenya and Tanzania in 1998.

American intelligence officials accuse the rebels’ spiritual leader, Sheik Hassan Dahir Aweys, of helping to shelter suspects in those attacks, and since 2007 U.S. forces have launched airstrikes at terrorist targets in Somalia.

After a week of heavy mortar and rocket attacks that have left at least 135 people dead and sent tens of thousands fleeing, the insurgents have moved to within a half-mile of the hilltop presidential palace in Mogadishu, the Somali capital, which is being guarded by African Union peacekeepers with tanks and armored vehicles.

The Islamists, reportedly joined by hundreds of foreign fighters, didn’t move on the palace Friday and almost certainly would lose a ground confrontation with the better-armed, 4,300-man peacekeeping force.

Still, Aweys, a veteran hard-liner who U.S. officials charge is linked to al Qaeda, vowed to topple the government and institute “the Islamic state of Somalia.”

Less than four months after a new, moderate Islamic government was formed in a country that’s been in the grip of civil war since 1991, the latest multimillion-dollar international plan to stabilize Somalia appears to be in tatters.

Despite a beefed-up African Union peacekeeping force and a U.N.-backed reconciliation effort, the moderate president, Sheik Sharif Ahmed, has failed to win the support of hard-liners such as Aweys or the powerful insurgent group al Shabaab, which the State Department has labeled a terrorist organization.

BY SHASHANK BENGALI

McClatchy News Service