BBC News political reporter, in Brighton
George Bush and the "right-wing neo-con establishment" have promoted a "clash of civilisations" between Muslims and the West, Ken Livingstone has said.
The London mayor made the remarks at a TUC fringe meeting in which he called for vigilance against a growing threat
from the British National Party.
He warned that if certain ideas were allowed to grow in a society, such as that a clash of civilisations was inevitable, then groups such as the BNP were able to exploit the situation.
Ken Livingstone has been a critic of the Iraq war
The BNP was in a similar position to France's Jean-Marie Le Pen's National Front 20 years ago, he said.
Le Pen pushed the socialist hopeful into third in presidential polls.
"Once they get to that point they remain a constant threat," he told a Unite Against Fascism meeting in Brighton.
But it is Mr Livingstone's comments about US foreign policy which are likely to be seen as the most controversial.
The US president is a close ally of UK prime minister Tony Blair, and the Labour mayor has been a vocal opponent of Britain's involvement in the war in Iraq.
The mayor also said that it was important to tackle any progress by the BNP who, he claimed, would exploit any opportunity to promote themselves.
In the past the far-right in Britain had focused on Jewish people, then on black people, and now Muslims were their target, he said.
Unions and government all had a role in tackling racism, he added.
And he gave the example of the London Fire Brigade in the early 1980s when he was leader of the GLC.
Then there were 7,000 firefighters, only seven of whom were black, he said, but the Fire Brigades' Union and others worked to tackle that issue.
Holding London up as a beacon of how racism could be taken on and how different races could live in harmony, he said: "You have to have mutual respect."