By Paul Reynolds BBC News Online World Affairs correspondent

President George W Bush's timetable for possible action against Iraq by the end of the year has been put into doubt by Iraq's unexpected acceptance of the UN demand for weapons inspectors to be allowed back in.

If the United States agrees to hold off while inspectors do their job, the threat of war goes away, probably for weeks, possible for months and maybe even a year.

If Iraq complies fully, of course, then there might not be a war at all.

But the US could go it alone, raising the prospect of action this winter.

And at any stage, if Iraq blocks the inspectors' work, the threat of war would return at once.

These are some of the indicators along the way:

Congressional approval

The current Congress is due to adjourn on 4 October though congressional adjournments are flexible.

Congressional elections are held on 5 November. Waiting for a new Congress would inject further delay and disrupt the momentum he has started.

Mr Bush says he is confident of getting approval but he will have to work for it.

United Nations backing

President Bush made his case before the UN General Assembly on 12 September. There was immediate unity in the Security Council about the need for a new resolution demanding Iraqi compliance.

But then Iraq agreed to comply before any resolution could be agreed.

This has thrown discussions into some confusion and the outcome is not certain.

Allied support

Allied support is regarded in Washington as valuable but not in the final analysis necessary.

The British Prime Minister Tony Blair is already shoulder to shoulder with George Bush and the French are showing some sympathy.

The Germans are not but they do not have a UN veto. The Russians and Chinese are sceptical but might sit on the sidelines. But they will probably insist on giving the inspections regime a chance first.

If inspections are blocked the whole UN could rally behind military action.

Arab support

The United States will need the help of at least Kuwait and Qatar to mount any major operation. This it seems to have. Otherwise support in the Arab world is thin..

Everything would change if Iraq stops proper inspections and the UN calls for action. Then, Arab countries would be more helpful.

Making the case

Britain has promised to release a dossier on Iraq's efforts to make weapons of mass destruction. This could come in the week of 23 September when Parliament is to be recalled for a debate. Britain issued a similar document making the case against the Taleban just before the war in Afghanistan.

Whether Washington does the same this time is an open question, but congressional leaders are already being privately briefed.

Logistics

The old adage about amateurs discussing strategy while experts discuss logistics comes into play. It will take weeks, perhaps three months or so, to get a sizeable force into position. A sizeable force means one of about 250,000 troops.

This could take until the end of this year or even the beginning of next. Even a more modest force of 50,000 would need several weeks to be positioned.

All this, of course, will coincide with the cool season, ideal for military operations, as it was in the Gulf War of 1991.

Ramadan

The Americans would probably like to avoid action during this holy month of fasting in the Muslim world. By chance, the dates for Ramadan this year are from early November to early December (depending on the appearance of the new moon) and this would fit in with a timetable for possible action thereafter.

There are, as always, some jokers in the pack. Mr Bush has not taken decisions on how to achieve his aim and others will come up with alternatives to an invasion.

Washington itself might hope for a quick strike against Saddam himself, leading to a collapse of his regime without a war.

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