Yemen's outgoing president, who last month agreed to transfer authority to his deputy, is in need of medical treatment that will require him to leave the conflict-torn country, the U.N. envoy to Yemen said on Wednesday.

Last month, President Ali Abdullah Saleh signed an accord to transfer his powers to his deputy, Abd-Rabbu Mansour Hadi, ushering in an opposition-led Yemeni government to lead the country to early presidential elections in February 2012.

There have been concerns among Western officials that Saleh might once again try to wiggle out of the deal aimed at easing him out of power in the Arab world's poorest nation. But it appears that medical necessity might force Saleh to vacate the country for a period of time.

My understanding is that President Saleh still requires serious medical treatment and medical treatment that he will require outside of Yemen, U.N. special envoy Jamal Benomar told reporters after privately briefing the Security Council.

Efforts are being made ... for arrangements to be concluded for him to get this treatment, he said.

Saleh was previously forced to seek treatment in Saudi Arabia for injuries suffered in an apparent assassination attempt in June after once again ducking out of a deal to relinquish power. The attack ushered in street battles that devastated parts of the Yemeni capital Sanaa.

SALEH'S DEPARTURE WOULD BE 'BENEFICIAL'

Benomar said the deal leading to an early election, in which Saleh will not be running, was gradually being implemented. He said he had no doubt there would be a presidential election on February 21, though he warned that the situation in Yemen was highly volatile.

One senior Western diplomat said on condition of anonymity that history and psychology suggest that (Saleh) will do everything he can to avoid sticking to the timetable for stepping aside.

However, the diplomat added that Saleh's need for medical treatment outside Yemen would be beneficial because it would remove him from the country for a period of time.

Last month U.N. Secretary-General Ban Ki-moon said that Saleh was planning to come to New York for medical treatment. In the end, Saleh never travelled to the United States.

Western diplomats told Reuters on condition of anonymity that Washington did not want to issue him an entry visa.

Earlier this week a dissident army general said he backed a peace accord signed last month, lending support to efforts to pull Yemen from the brink of civil war.

If the deal goes according to plan, Saleh will become the fourth Arab ruler brought down by mass demonstrations that have reshaped the political landscape of the Middle East.

Yemen's transitional government faces challenges from a southern separatist movement that wants to revive the Yemeni socialist state that existed before Saleh united it with the capitalist north under his rule in 1990 and al Qaeda-linked militants who have seized territory in the south.

Months of protests against Saleh's rule have alarmed Saudi Arabia and the United States, which had seen Saleh as a bulwark against al Qaeda in the region.

Top oil exporter Saudi Arabia shares U.S. fears that more instability in Yemen could embolden the country's al Qaeda wing against which Washington has waged a campaign of drone strikes -- in a country sitting next to key oil shipping routes.

(Reporting By Louis Charbonneau; Editing by Eric Beech)