By Nick Assinder BBC News Online political correspondent

The BBC's Iraq: Britain Decides day is featuring a range of programmes and events to reflect views and opinions on the possible war with Iraq.

To mark the event, BBC News Online charts how the Iraq crisis is leading to what could be the biggest gamble of Prime Minister Tony Blair's career.

Tony Blair has admitted that he is risking everything on his determination to rid Saddam Hussein of weapons of mass destruction.

And few who have seen him pressed about his apparent tunnel vision doubt that he really believes what he is doing in support of his closest ally George Bush is right.

Probably for the first time in his premiership, he is prepared to fly in the face of public, world and even his own party's opinion.

And despite a campaign of persuasion over the past few months, he has so far signally failed to win over the vast majority of his critics on this issue.

If this all goes wrong for Mr Blair he will be in very serious trouble indeed

Indeed, the current crisis in Nato and widening splits within Europe over the looming war suggest the crisis is escalating.

If this all goes wrong for Mr Blair he will be in very serious trouble indeed.

It is not too extreme to suggest - as some of his own MPs do - that his leadership will be on the line.

And, as the BBC focuses an entire day on the issue now dominating the headlines, many are beginning to ask whether the prime minister has actually lost the plot over this particular issue.

'Poodle' jibes

Many of his MPs are furious at what they see as Mr Blair's submissive relationship with the US president over Iraq.

The 'poodle' jibes sting him, but the prime minister's attempts to suggest that he is acting as a restraining influence on the president are widely dismissed as spin.

Similarly, his ambition to use his admittedly powerful position to provide an historic bridge between Europe and the US now looks doomed, at least in the short term.

His critics are most vehemently opposed to any action against Saddam Hussein without first giving the weapons inspectors more time, and then without winning a second UN resolution.

Blair is seen as submissive to Bush

They are not convinced by the current evidence against Saddam. What some see as stunts like the recent dossier, lifted from the internet, only serve to strengthen their view that the government is attempting to spin them into a war.

Suggestions from Mr Blair that there are limited circumstances in which he would go to war without the UN bolster the view that he and President Bush have already made up their minds.

Many are also dismayed that the prime minister is displaying the sort of personal belief over this issue that they believe is lacking from him over domestic issues such as the health service.

And, while they still may be a minority on the backbenches and in cabinet, the critics appear to speak for the public.

But, up to now, the prime minister has clearly believed this is another battle he can win.

He has remained confident that he will get his second UN resolution and that will win over the vast majority of his opponents.

Decision time

Those left would simply be hardened anti-war-at-any-price campaigners who he feels he can dismiss.

Even if public opinion remained against him, he also knows that once British troops are laying their lives on the line in Iraq, that opinion will be transformed overnight.

That has clearly been his calculation. Up to now.

There is now real concern in Downing Street that a second resolution may prove impossible without a further delay of many weeks

But there is now the real possibility that he will not be able to win over the UN in the sort of time frame president Bush clearly has in mind.

The Franco-German alliance, bolstered by Russia, can effectively veto any planned action.

And, probably for the first time, there is now real concern in Downing Street that a second resolution may prove impossible without a further delay of many weeks.

That would leave Mr Blair exposed. The president is clearly not ready to consider any further delays and, should that be the UN demand following Friday's report by the weapons inspectors, Mr Blair will have to make a crucial decision.

He may finally have to chose between the UN and the US.

And if he goes to war alongside president Bush under those circumstances he will be taking by far the biggest gamble of his political career.

And for a man who normally does nothing without the backing of focus groups and opinion polls, that would be uncharted and highly dangerous territory.