Libyan leader Muammar Gaddafi has vowed to pursue his vision of a United States of Africa, in his inaugural address as the new chairman of the African Union.
Col Gaddafi was elected by the heads of state of the 53-member union behind closed doors at a summit in Ethiopia.
A BBC correspondent at the summit says Col Gaddafi was seen to be the obvious choice, but some delegates are uneasy about his nomination.
Col Gaddafi replaces the Tanzanian President, Jakaya Kikwete.
Wearing a golden brocade robe and cap, Col Gaddafi sat with the traditional African leaders who accompanied him at the front of the room, rather than in the seat for the Libyan delegate.
"I shall continue to insist that our sovereign countries work to achieve the United States of Africa," he said in his inaugural speech.
But he admitted that African leaders were "not near to a settlement" on the issue.
He told fellow summit leaders that his unity project would be approved at the next meeting in July unless there was a majority against it, reports the BBC's Elizabeth Blunt from Addis Ababa.
The AU normally relies on consensus in reaching decisions, but Col Gaddafi introduced what he described as the Islamic concept that "silence is approval," she said.
Under this principle, at least two-thirds of AU leaders would have to actively oppose Col Gaddafi's proposals, rather than simply ignoring his ideas, she added.
But an expert on the African Union called the vision of the United States of Africa a "ludicrous fantasy on the part of [Col] Gaddafi."
Kathryn Sturman at the South African Institute of International Affairs said many African leaders would not be prepared to give up their national sovereignty to join the proposed single-state federation proposed by the Libyan leader.
Ms Sturman said the chair of the group does not have any singular decision-making power, and cannot push through any changes without the consensus of the other leaders.
During closed-door talks on Sunday, African leaders again postponed Col Gaddafi's dream of closer union.
In a compromise, the summit agreed to transform the African Union Commission - which oversees the AU - into an AU authority with a broader mandate, outgoing chair Mr Kikwete said.
"In principle, we said the ultimate is the United States of Africa. How we proceed to that ultimate - there are building blocks," Mr Kikwete said.
Malawi's President Bingu wa Mutharika said governments wanting greater unity could go ahead on their own, without worrying about splitting Africa.
The chairmanship of the African Union is a rotating position held by heads of state for one year.
It was the turn of a North African leader to chair the bloc, and Col Gaddafi was the only one present.
However, some African leaders believe the Libyan leader is too erratic to be AU chairman.
Before he arrived at the summit, he circulated a letter saying he was coming as the king of the traditional kings of Africa, our correspondent says.
Last August, he had a group of 200 traditional leaders name him the "king of kings" of Africa.
The summit's main agenda - to boost Africa's energy and transport networks - was pushed largely to the fringes, weighed down by the grim realities of the global economic downturn.