The Senate's confirmation of Conille, 45, a medical doctor and U.N. development expert, followed approval from the lower house of parliament last month.

It was Martelly's third attempt to install a new head of government. His first two nominees were rejected by lawmakers in June and August. This had raised concerns among diplomats and donors who said the poor Caribbean state desperately needed a working government to rebuild from a devastating 2010 earthquake.

Both houses of Haiti's parliament are dominated by senators and deputies whose parties fielded rival candidates to Martelly in a turbulent two-round presidential election that he finally won in a March run-off vote.

Conille's approval in the Senate, after a prolonged debate, came by a 17-3 vote. Nine lawmakers abstained, according to Senate President Rodolphe Joazile.

Haiti, known for decades of dictatorship, corruption and instability, faces a huge reconstruction task after last year's earthquake, which killed tens of thousands of people, and a lingering cholera epidemic that has claimed more than 6,000 lives.

WORKED WITH BILL CLINTON

Conille, who has a long career with the United Nations specializing in development and health issues, brings useful recent experience to the post, having worked as chief of staff to former U.S. President Bill Clinton in the latter's role as special U.N. Haiti envoy.

This role had involved helping to coordinate the huge international humanitarian response to the Haitian quake and working with donors on the delivery of aid.

Haitian authorities estimate the January 2010 earthquake killed more than 300,000 people and wrecked much of the capital, Port-au-Prince.

Pressing tasks for the new government include effectively fighting the cholera epidemic. It must also try to provide shelter for tens of thousands of earthquake survivors who are still living in makeshift tent camps vulnerable to hurricanes and floods.

"The country needs a government," said Senator Wencesclass Lambert, a member of the majority Inite party, who cast his vote in support of Conille on Tuesday night and called his approval "an important step" toward national recovery.

"There are so many people suffering," Lambert said. "International donors are reluctant to release funds if a new government is not in place."

In a final hurdle toward confirmation in his post, both houses of parliament will have to approve Conille's proposed plan for government.

But that is viewed largely as a formality, parliamentary sources said. They said Conille was now expected to be sworn into office swiftly, after addressing the Senate and the House separately to outline his plan as early as sometime later this week.

(Reporting by Joseph Guyler Delva; Editing by Will Dunham)