By Ahmed Mohamed

BAIDOA, Somalia (Reuters) - Somalia's parliament swore in Nur Hassan Hussein as prime minister on Saturday, hoping to bolster an interim government weakened by months of political deadlock and battles against insurgents.

The parliament almost unanimously voted to endorse President Abdulallhi Yusuf's nomination for premier in Baidoa, the southern trading town where Somalia's assembly sits.

"I promise that I will perform my duties honestly and respect the interim federal charter, and I ask the parliament to support me and correct me if I go wrong," Hussein told lawmakers moments after he was sworn in.

Yusuf urged the Italian-trained lawyer and long-serving Somali Red Crescent officer to quickly form a new cabinet.

"I am optimistic that the government will fulfil its obligations in the two years left for us," Yusuf told parliament.

The president announced Hussein's nomination on Thursday three weeks after his unpopular predecessor quit, caving into pressure over a feud with Yusuf and criticism over a lack of progress in building the transitional government.

Seen as a neutral political figure, Hussein's challenge lies in bringing unity to Somalia where 1 million people have been uprooted by fighting between Islamist insurgents and government troops, backed by the Ethiopian military.

Many Somalis are waiting to see if Hussein will seek talks with the anti-Ethiopian insurgents to end the conflict -- punctuated by almost daily roadside bombings, grenade attacks and shootings -- that has killed thousands this year.

The humanitarian crisis is said by the United Nations to be worse than Sudan's Darfur region.

On Friday, a spokesman for a group of Somali dissidents was sceptical about Hussein's ability to make a difference, saying the core problem was Ethiopia's "occupation" of Somalia.

Known as Nur Adde, Hussein was born in 1938 and served in many government jobs before rising to attorney general in 1987.

The self-confessed bookworm has been secretary-general of the Somali Red Crescent since 1991 when warlords toppled military dictator Mohamed Siad Barre and carved the Horn of Africa country into a patchwork of personal clan fiefdoms.

U.N. Secretary-General Ban Ki-moon welcomed Hussein's nomination, his spokeswoman said in a statement.

"The Secretary-General welcomes Mr Nur Hussein's background and experience in humanitarian operations in Somalia and thus his unique understanding of the challenges confronting his country," the statement read.