The British Government is to delay a decision on whether to support London's bid to host the 2012 Olympics, a spokesman said today.

The Cabinet was due to make a decision on Thursday following a presentation from Culture, Media and Sport Secretary Tessa Jowell.

While that presentation is still set to go ahead, Prime Minister Tony Blair's official spokesman said the Cabinet would need time to "mull over" a final decision.

"There will be a substantive discussion at the Cabinet tomorrow (Thursday) where Tessa Jowell will lead colleagues through the arguments and through the detail," the spokesman said.

"Some of it will be new to colleagues around the table and it seems only sensible that they have a period of time in which to reflect on and mull over what they hear tomorrow."

The spokesman's comments mean a decision on the London bid is not now expected until next week's Cabinet meeting on February 6 at the earliest.

It is believed the crisis over Iraq - straight after Thursday's cabinet meeting Blair flies to the US for talks on the issue with President George W. Bush - has also influenced the delay, as an Olympic announcement might appear inappropriate amid a backdrop of growing world tension and uncertainty.

Sources stressed, however, that possible delays would not mean Blair was less likely to approve a London bid.

Today reports suggested the London bid may get a STG1.5 billion ($A4.2 billion) boost from a new lottery game.

The cost of staging the London Games is estimated to be STG2.6 billion ($A7.28 billion).

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