“If confirmed, I pledge to fulfil the president’s vision of working in close partnership with the United Nations,” said John Bolton during an often tough Senate confirmation hearing.

Mr Bolton has been an outspoken critic of the UN and Democrats have denounced his selection due to his past criticism of the organisation.

“Frankly, I’m surprised that the nominee wants the job, given all the negative things you’ve said about it,” the panel’s top Democrat, Joe Biden said, who also likened Mr Bolton’s nomination to “sending a bull into a china shop”.

Mr Bolton, 56, who for the past four years has been the undersecretary for arms control and international securtiy affairs, is considered by supporters to be a brilliant policy analyst.

However critics fear his hawkish leanings may make him unsuitable for a job where he has to work with other countries he has criticised, and he has frequently dismissed the organisation as corrupt and irrelevant.

In one of his most controversial remarks, he once remarked that if the UN headquarters in New York “lost 10 stories, it wouldn’t make a bit of difference”.

He told the Senate Foreign Relations Committee he strongly believes the UN needs US leadership to be effective, adding, “I deeply believe that”.

“Now more than ever, the UN must play a critical role as it strives to fulfil the dreams and hopes and aspirations of its original promise to save succeeding generations from the scourge of war, reaffirm faith in fundamental human rights and to promote social progress and better standards of life in larger freedom,” he said.

“This effort demands decisive American leadership, broad bipartisan support and the backing of the American public,” he added.

Mr Bolton listed his four main priorities if confirmed in the role: to strengthen UN institutions, stem the proliferation of weapons of mass destruction, support the global war on terrorism and address humanitarian crises such as the spread of HIV/AIDS.

He dismissed allegations he was responsible for the dismissal of two intelligence analysts who disagreed with his assessment of a Cuban weapons programme.

Last month almost 60 former US diplomats sent a letter to the Foreign Relations Committee strongly opposing Mr Bolton for the post.

However five Republican former US Secretaries of State this month lobbied in his favour.

Mr Bolton is known as being tough-minded and his boss, Secretary of State Condoleezza Rice said he has a proven track record of effective multilateralism.

“We’ve asked John because he gets things done,” she said.