Iraq's offer to readmit weapons inspectors must be viewed "with a high degree of scepticism", UK Foreign Secretary Jack Straw has said.

But his warning comes as a divide begins to emerge between world powers over how to respond to the offer.

Mr Straw echoed the White House's sceptical stance, but Russia is urging nations to take the offer at face value - and the Iraqi's at their word.

In a letter to United Nations Secretary General Kofi Annan, Iraq claims the offer to allow the unconditional return of weapons inspectors has removed any justification for military action.

Straw: New UN resolution still needed

But the UK and the US remain unconvinced.

Aside from the offer on the table, Mr Straw is still calling for a new UN resolution to be drawn up about Iraq's alleged build-up of weapons of mass destruction.

Meanwhile Labour MPs Tam Dalyell and Alice Mahon, leading backbench opponents of military action against Iraq, have described the offer as a "litmus test" for US President George Bush.

They said: "His response will signal whether the US is acting through concern over weapons of mass destruction or if it is intent on oil acquisition and regime change."

Downing Street has said people should remember Saddam Hussein's history of "playing games" over weapons inspections.

Threat

Mr Straw went to Number 10 on Tuesday to brief Prime Minister Tony Blair about his visit to the UN last week.

He said: "This apparent offer is bound to be treated with a high degree of scepticism by the international community."

Particularly, he said, because it came only four days after the Iraqi Deputy Prime Minster, Tariq Aziz, had said precisely the opposite.

The text of the proposed UN resolution has yet to be drawn up.

But Mr Straw said it would focus on the threat posed by the "Iraqi regime from their possession and their use of weapons of mass destruction".

Saddam Hussein has conducted brinkmanship too often in the past

Menzies Campbell, Lib Dem foreign affairs spokesman

UN weapons inspectors left Iraq in 1998 complaining that they had not been given unrestricted access and have not been allowed back.

Glasgow MP George Galloway, who is visiting Iraq, told BBC Radio 4's Today programme the offer should be "grabbed with both hands".

The Conservatives backed Mr Straw's call for a fresh UN resolution setting out clear deadlines, despite the latest offer.

Shadow foreign secretary Michael Ancram said: "We have seen all of this before - and Saddam is merely playing games with the international community."

Liberal Democrat foreign affairs spokesman Menzies Campbell echoed Mr Ancram in stressing that inspectors must be allowed to look in "every nook and cranny".

"Saddam Hussein has conducted brinkmanship too often in the past for this development to be treated with caution, not optimism," said Mr Campbell.

The offer came after Mr Blair stepped up efforts to persuade MPs to back him over Iraq, amid claims he faces a backbench rebellion against possible military action.

Halifax MP Alice Mahon claimed in the Independent newspaper that up to 100 Labour backbenchers would rebel against the government's policy.