ABUJA — A top US envoy on Tuesday highlighted the "uncertainty" in Nigeria where political turmoil has mounted while the country's ailing president is treated abroad.

US Assistant Secretary of State for Africa Johnny Carson met Vice President Goodluck Jonathan for talks as the two chambers of Nigeria's national assembly voted for Jonathan to take on President Umaru Yar'Adua's powers.

"The Secretary of State (Hillary Clinton) wanted me to clearly convey that during this period of uncertainty we believe that it is very important that if indeed there is a transition of political power in Nigeria let it be done democratically," Carson told reporters after the meeting.

"As a fellow democracy, US believes firmly in the values of democracy.

"We think that its principles are also important in Nigeria, which is Africa?s largest democracy and also a friend and a partner of the US," he said.

Carson said he had a "very good meeting" with Jonathan to discuss developments in Nigeria and Africa in general.

Carson, who arrived Nigeria on Saturday, said President Barack Obama and Clinton expressed their sympathies over the hospitalisation of Yar'Adua in Saudi Arabia since November 23.

Carson said the need for electoral reforms in Nigeria after a series of flawed elections in Africa's most populous country, featured in his talks with Nigerian authorities.

"We talked a little bit about elections in the US, which is also committed to working with Nigeria on helping to improve the electoral process," he said.

Nigeria is the final leg of a four-nation west African tour which has taken him to Ghana, Togo and Benin.

AFP