British Prime Minister Tony Blair, who last week visited Russia, Pakistan and India, is now in the Gulf state of Oman to rally support for US-led military operations in Afghanistan.

But what lies behind Mr Blair's remarkable display of energy and personal commitment?

It is frequently said that Britain is America's closest ally and has a special relationship with it.

At the start of the crisis, Tony Blair wanted to make sure that western Europe was fully behind the United States, but on this occasion his efforts were hardly necessary.

Mr Blair clearly decided he could make a major contribution.

Shuttle diplomacy was not something George W Bush was going to get personally involved in: American presidents do not usually travel at times of crisis.

According to one American newspaper, Mr Blair was thus appointed as ambassador of the US.

It does not appear to have been a formal division of labour.

Senior American officials say the two leaders are committed to the same agenda and get on with carrying it out in their own way, though they consult.

But Mr Blair did not have to be as energetic and high-profile as he is; he is not simply carrying out American instructions.

Moral purpose

Sometimes he has gone beyond American policy, setting out an ambitious programme for healing all the ills of the world.

Mr Blair's sense of moral purpose, his conviction that the campaign against terrorism is a just cause, gives his interventions a special flavour.

He is of course a practising Christian, and may think that speaking to Muslims from a position of faith - albeit a different faith - carries greater conviction.

Mr Blair has reputedly been studying the Koran; in a speech last week he said Bin Laden was no more true to his religion than the Christian crusaders who pillaged and murdered in the Middle Ages.

In his visits abroad, Mr Blair is also seeking to exploit Britain's historical links with countries that used to be its colonies.

But his prominence in the campaign does increase the risks to himself and his country: one hardline Islamic group is alleged to have said Mr Blair was now a legitimate target.