MOGADISHU, Somalia - Somalia's U.N.-backed government was crumbling yesterday as the president defied parliament and as Kenya announced sanctions against him in a strong public rebuke.

President Abdullahi Yusuf unilaterally fired Prime Minister Nur Hassan Hussein this week after months of public feuds over the best way to bring peace, but parliament soundly rejected Yusuf's decision and voted to keep the prime minister.

Yesterday, Yusuf announced he was appointing a former interior minister, Mohamed Mohamud Guled, as the new prime minister.

Hours later, Kenyan Foreign Affairs Minister Moses Wetangula called Yusuf an obstacle to peace and announced sanctions, including a travel ban and freezing any assets in Kenya. "The region and international community should act in unison to collectively condemn all spoilers to the Somali peace process," Wetangula told journalists.

It was not clear when the sanctions would go into effect, but they are a powerful charge because Kenya hosted the two-year-long peace talks that formed Yusuf's government in 2004.

The government dispute does nothing to stabilize the administration, which wields virtually no authority in the face of powerful Islamic insurgents who have taken over most of the country.

Civilians have suffered most from the violence surrounding the insurgency, with thousands killed or maimed.

The United States worries that Somalia could be an extremist breeding ground, and accuses the most powerful Islamic faction, al-Shabab, of harboring the al-Qaeda-linked extremists who blew up the U.S. embassies in Kenya and Tanzania in 1998. Somalia's lawlessness has also allowed piracy to flourish off the coast; bandits have taken in at least $30 million in ransom this year.

In Washington yesterday, Deputy State Department spokesman Robert Wood said Yusuf's actions "undermine the transitional national government's efforts to promote peace and stability in the region, so this is a concern to us."

Somalia has been without an effective government since 1991, when warlords overthrew a dictatorship and then turned against one another.