London, Nov 12: Amid fears that al-Qaeda terrorists might use the cover of huge anti-war protests to disrupt US President George Bush's three-day visit commencing here on November 18, the metropolitan police have launched the biggest security operation Britain has seen for any visiting head of state. British Prime Minister Tony Blair, a staunch ally of Bush, is struggling to prevent anti-war protesters from causing a full-scale security crisis during the US President's visit.

President Bush is the first US President to be offered a state visit to Britain. The Queen has met all 11 presidents who have come to power during her reign. The White House regards London as a high-risk target for a suicide attack. Militant cells of mainly North African extremists are known to operate in Britain.

The President and his wife, Laura, will be guests of the Queen from Wednesday to Friday next week.

The 'stop the war coalition', which is organising a series of protests, said today that despite police plans to set up an exclusion zone, it would demand the right to march down Whitehall, the seat of power. Bureau Report