Calling on the world body to “grow and take on new roles” and to “develop and deliver on new fronts,” Mr. Ban told the Royal Institute of International Affairs in London that the UN was well placed to tackle issues ranging from climate change to disarmament.

“You will know that our world of complex and global challenges is exactly the environment in which our United Nations should thrive – because these are challenges that no country can resolve on its own,” he said.

The Secretary-General stressed that it was unrealistic to expect the UN to provide a solution to every challenge.

“But we can, and should, serve as a forum to set a global agenda and consensus. We can, and should – given the necessary political resolve – implement the clearly defined will of the international community. We can, and should, be visionary and proactive.”

To deal with this, the world needs greater dialogue, patience, resources and reform, he said.

During his address to the Royal Institute, Mr. Ban outlined the major priorities facing the UN in the three pillars of its work: peace and security, development and human rights.

He said the crises in Darfur, the Middle East, Lebanon and Iraq are at the top of his peace and security agenda, as well as efforts to fight terrorism and to overcome the current stalemate in disarmament and non-proliferation, particularly regarding the Democratic People’s Republic of Korea (DPRK) and Iran.

Turning to development, he urged Governments to take more concerted action towards meeting the Millennium Development Goals (MDGs), the set of eight targets for slashing poverty and other social and economic ills, all by 2015.

Mr. Ban also called on leaders to “accept their historical responsibilities” towards future generations and reach concrete agreements on reducing emissions and other ways of combating climate change.

“I am convinced that this challenge, and what we do about it, will define us, our era, and ultimately, our global legacy. It is time for new thinking.”

He added that greater attention must be paid to human rights, so that it is a pillar of the UN’s work “not only on the drawing board, but in reality, on the ground.”

The Human Rights Council, introduced last year to replace the discredited Commission on Human Rights, must be scrutinized “to ensure that it delivers on its promise and shines a spotlight on the darkest places in the world.”

Mr. Ban also detailed some of the internal UN reforms he has introduced to strengthen the world body’s capacity, especially in peacekeeping as the number of UN personnel in the field reaches a historic high of nearly 100,000.

While in London today, Mr. Ban held talks with the new British Prime Minister Gordon Brown.