WASHINGTON / LONDON

America has asked Britain to draw up plans for 25,000 of this country's troops to join a US task force to overthrow Saddam Hussein. In a move which reveals advanced US plans for the next phase of its war on terror, Government departments are considering the plans ahead of Vice-President Dick Cheney's meeting with the Prime Minister today.

The request for such a large number of British troops shows the high stakes America is now playing for. It will alarm Cabinet doves, thought to include Clare Short, the International Development Secretary, and Robin Cook, the former Foreign Secretary and now Leader of the Commons.

The UK Government is already facing a split on the issue of military action against Iraq. One Minister described those who had questioned Blair's policy of fully backing a US military campaign as 'appeasers'. 'At some point people have to realise that action has to be taken,' he said.

The request for such a large number of troops is unprecedented in peacetime. It is one of three major options now being considered by the Government which has always insisted publicly that no final decisions have been made on military action against Saddam.

British troops would be part of a 250,000-strong ground force to invade Iraq in an operation similar to Desert Storm in 1991.

The second option is one where smaller special forces units would support opposition forces within Iraq, like the tactic used in Afghanistan, where the Northern Alliance was backed with air strikes and logistical support in its battle to overthrow the Taliban.

The third option - thought to be preferred by the Foreign Office - is one of 'aggressive containment'. Under this plan, air strikes against Iraq would be intensified if Saddam did not agree to a comprehensive inspections agree ment.

America is confident that with enough evidence against Saddam, the White House can persuade other Arab states to support military action. 'I think they all have legitimate concerns about the regime in Iraq, and they're aware that Saddam continues to represent a threat to the security and stability of the region,' said one White House official. 'I expect they'll all want to talk about it.'

America has already begun a discreet military build-up in preparation for a ground war in Iraq. US special forces are training Iraqi militia to be ready for a strike against Saddam in the coming months.Teams of instructors drawn from American elite regiments have been arriving in Kurdish-held areas in the north of Iraq in recent weeks, targeting the semi-autonomous areas run by the Kurdish Democratic Party. The instructors are improving local fighters' tactical and weapons skills and teaching them how to exploit chaos caused by American air strikes. They are also drawing up lists of potential targets, a vital prerequisite to any ground offensive.

Defence sources say a battalion of 24 Longbow Apache attack helicopters also recently arrived in Kuwait. The helicopters, capable of operating up to 250 kilometres behind enemy lines, could be used to attack air defence sites and Iraqi armour in the opening air phase of any war.

In a separate development sources say more than 5,000 US fighting vehicles, mothballed in Kuwait since the end of the Gulf War, have quietly been overhauled.