The US and Britain are to take military action by themselves against Osama bin Laden, prime suspect behind last week's terrorist atrocities, and his protectors in Afghanistan.

According to senior British officials, President George W. Bush and Tony Blair, the UK prime minister, agreed that a tight command structure was needed and that the military operation should be undertaken largely, perhaps wholly, by their own forces. The White House declined to comment. However, one lesson US military planners took from Nato's bombing campaign in Kosovo in 1999 was that a large alliance complicated and delayed the choice of objectives.

The agreement between the two leaders came in meetings at the White House on Thursday, before Mr Bush delivered his address to Congress.

In the speech, widely praised by political supporters and opponents, Mr Bush delivered an ultimatum to Afghanistan's Taliban rulers to hand over those connected to Mr bin Laden's network and to close down terrorist bases. The Taliban, he said, "will hand over the terrorists or they will share in their fate".

But on Friday the Taliban reiterated its refusal to hand over Mr bin Laden unless Washington provided clear proof of his guilt in last week's attacks.

Abdul Salam Zaeef, Afghanistan's ambassador to Pakistan, read a statement issued by the Taliban's leading Muslim clerics warning that any attempt by the US to launch an attack on Afghanistan would be met with jihad, or holy war. In northern Afghanistan, an upsurge of fighting was reported between Taliban and opposition forces seeking revenge for the recent assassination of their leader and taking advantage of threats of US strikes.

President Jacques Chirac indicated this week that France was willing to take part in any military campaign but it was not yet clear what role, if any, the French would play.

Countries that do not take part in the initial military action would be expected to take part in other phases of the war against terrorism, involving efforts to destroy the organisation and freedom of movement of terror groups and cut off their funds, UK officials said.

The military action would include a difficult search-and-destroy operation in mountainous terrain, involving special forces.

Mr Blair, along with other European leaders, is pressing Mr Bush to reject the view of hawks in his administration calling for strikes against other countries harbouring terrorists, at least at this stage, for fear of weakening the international coalition of support.

On Friday night European Union leaders unequivocally backed any US military action carried out by the US and agreed on a package of anti-terrorist measures.

European Union leaders meeting in Brussels agreed on Friday to support "targeted" attacks at countries that harbour terrorists.

Additional reporting by Judy Dempsey in Brussels, Andrew Jack in Moscow, and Edward Luce and Farhan Bokhari in Peshawar, Pakistan