British Prime Minister Tony Blair (search) on Thursday strongly endorsed the leadership of United Nations Secretary-General Kofi Annan (search), who is under fire over allegations of kickbacks and bribes in the U.N. Oil-for-Food (search) program.

Blair welcomed Annan's call for the U.N. to be reformed and said despite personal and political difficulties, he has been "a tremendous unifier" for the international community.

"It is been a tough time in the international community and it has been a very tough time for the United Nations Secretary-General," said Blair, launching a London seminar on UN reform which Annan addressed.

"I happen to think in that very tough time that he has handled himself with great distinction, with a lot of wisdom and in difficult circumstances has been a tremendous unifier.

"I know very it has not always been easy for him politically or personally but Kofi I wanted to say to you how pleased we are to have you here and how warmly we welcome you and how much we regard your Secretary-Generalship of the United Nations," he added.

The London seminar is regarded as a strong endorsement of Annan's reform agenda. While President Bush twice refused to back Annan amid calls for his resignation, Blair has strongly supported the secretary-general.

Annan is pushing for major U.N. reforms, including an expansion of the Security Council. But there are concerns that allegations of widespread corruption in the program that allowed deposed Iraqi President Saddam Hussein's government to sell oil and use the proceeds to buy food, medicine and other humanitarian goods, could derail the plans.

Addressing the seminar, Annan insisted the United Nations had an important role to play in world affairs, but needed improvement.

"You see the world does need a forum for collective decision-making and it needs an instrument of collective action," said Annan.

"Our founders intended the United Nations to be both those things. Our task is to adapt and update it so that it can perform those functions in the 21st century," he added.

Annan noted that he had "just under two years" left to serve. "As I look ahead to the remainder of my term, I feel a real sense of excitement and commitment," he said, adding that priorities would be carrying through U.N. reforms, tackling poverty in the developing world, the transition to democracy in Iraq and the Middle East peace process.

Several U.S. congressional committees have been investigating allegations of corruption in the Oil-for-Food program. Concerns about Annan's leadership deepened with the release of an interim report last week, led by former U.S. Federal Reserve Chairman Paul Volcker (search), which criticized U.N. management of the program.

Annan said he wanted action on two U.N. reports published recently.

A high-level panel report called for sweeping reform of the United Nations in the wake of bitter divisions over the U.S.-led war in Iraq. It called for an expanded and more active Security Council with authority to take action to prevent conflicts or potential genocides.

A second report spelled out the investments needed to meet U.N. goals adopted by world leaders at the Millennium Summit in 2000 to tackle poverty, hunger and disease mainly in African and Asian countries.