The former US Secretary of State, James Baker, has warned the Bush administration that it would be very risky and expensive to mount an invasion of Iraq - especially if the White House decided to go it alone.

Writing in the New York Times, Mr Baker - who played a key role in building the coalition that drove Iraqi forces out of Kuwait in 1991 - said using military force was the "only realistic way" to change the regime in Baghdad.

James Baker: A key player during the 1991 Gulf crisis

"Although the United States could certainly succeed, we should try our best not to have to go it alone, and the president should reject the advice of those who counsel doing so," he said.

"The costs in all areas will be much greater, as will the political risks, both domestic and international, if we end up going it alone or with only one or two other countries."

Mr Baker served in the 1988-92 administration of the president's father, George Bush, and is a key political ally of the current president.

He is the latest in a series of prominent US officials - including other influential Republicans - who have warned President Bush against unilateral military action to topple Iraqi President Saddam Hussein.

'Fractious country'

After the 1991 Gulf War many analysts argued that coalition troops should have gone all the way to Baghdad to oust Saddam Hussein and annihilate his forces.

It cannot be done on the cheap - it will require substantial forces and substantial time James Baker

Mr Baker warned that a new operation to topple Saddam Hussein would probably result in more casualties than in 1991.

"We will face the problem of how long to occupy and administer a big, fractious country and what type of government or administration should follow."

And he stressed that the US administration must pursue a united policy on Iraq, he stressed.

"The president should do his best to stop his advisers and their surrogates from playing out their differences publicly and try to get everybody on the same page."

Settlement withdrawal

Mr Baker said the perception of US policy on the Arab-Israeli conflict was undermining efforts to oust Saddam Hussein.

Israelis fear they could be targeted by Iraq again

He urged the Bush administration act boldly in a "fair and balanced way" to resolve the Arab-Israeli dispute.

"That means, of course, reform by Palestinians and an end to terror tactics. But it also means withdrawal by Israeli forces to positions occupied before September 2000 and an immediate end to settlement activity."

The US must also press for a new United Nations resolution "requiring that Iraq submit to intrusive inspections anytime, anywhere, with no exceptions, and authorising all necessary means to enforce it", Mr Baker said.

Senior US administration officials have argued that even a return of weapons inspectors to Iraq will not guarantee that Saddam Hussein's military ambitions are reined in.