ALEX Salmond has urged the Chilcot Inquiry to examine claims in a newly published memo that suggested Tony Blair gave backing to a planned US invasion of Iraq a year before MPs voted on it.

American secretary of state Colin Powell said in a secret document in 2002 that the then Labour prime minister had signalled he "will be with us should military operations be necessary".

It came before discussions about how to deal with Saddam Hussein's regime between Mr Blair and US President George Bush at his ranch.

According to reports, Mr Powell wrote: "Blair continues to stand by you and the US as we move forward on the war on terrorism and on Iraq ...

"Blair knows he may have to pay a political price for supporting us on Iraq, and wants to minimise it.

"Nonetheless he will stick with us on the big issues."

SNP MP Alex Salmond said: "The memo contradicts claims from Mr Blair that all that time he had been seeking diplomatic ways to avoid an invasion," said the SNP's foreign affairs spokesman at Westminster.

"It also adds weight to the evidence given by Sir Christopher Meyer - the former UK ambassador to the United States - to the Chilcot Inquiry that the military timetable and preparation for invasion took precedence over any diplomacy and specifically over the timetable for the weapons inspectors led by Hans Blix.

"The Chilcot Inquiry has still to be published and these revelations will need to be looked at very seriously.".

The ex-premier told the Chilcot Inquiry that Mr Bush would have understood he was ready to support military action if the diplomatic route was exhausted.

The briefing note, prepared for Mr Bush in March 2002 ahead of his Crawford summit with Mr Blair later that year, emerged after a court ruling in the US led to the publication of thousands of emails received by Hillary Clinton.

Former Liberal Democrat leader Sir Menzies Campbell said the content of the memo did "not come as a surprise".

"This is yet more confirmation, if any was needed, that Tony Blair in spite of what he said publicly and in the House of Commons at the time had made up his mind willy nilly to support George W Bush whatever the circumstances," he said.

"I have no doubt that even at this stage the Chilcot Inquiry will regard this as a remarkable piece of information."

A spokesman for Mr Blair told the content was consistent with what he had said publicly before.