President Bush will spend today putting the final touches to his controversial plan to escalate the war in Iraq as he enters what Washington analysts have described as some of the most important days of his presidency.

White House staff were reported to be debating whether Mr Bush should address the nation tomorrow night from the Map Room, made famous by Franklin Roosevelt during the Second World War — a conflict that Mr Bush has referred to several times in speeches about the War on Terror — or from the Oval Office, the usual venue for presidential speeches.

The decision is part of the careful staging of Mr Bush's presentation, in which he is expected to announce the unpopular deployment of 20,000 additional soldiers to Iraq while simultaneously attempting to win the support of a Democrat-controlled Congress and a sceptical public.

After the speech, which will be broadcast on primetime television and last 25 minutes, the President will fly to Fort Benning, Georgia, a massive army base considered the home of the US infantry, for a less formal address and what is likely to be a warm reception. On Friday, the US Secretaries of State and Defence, Condoleezza Rice and Robert Gates, will describe their support for the plan in testimony before Congress.

"The world really is watching and it is important to get this right," said Tony Snow, the White House press secretary.

The initial selling of the strategy began last night with the invitation of 30 Republican Senators to the White House, American press reports said today.

The Washington Post quoted those present at the meeting saying that Mr Bush had decided to send additional soldiers and that the President was confident of the support of the Iraqi Prime Minister, Nouri al-Maliki, in carrying the fight to those causing sectarian violence in Iraq, including the Shia militias who are seen as exerting a large influence over the government.

"It was clear to me that a decision has been made for a surge," Senator Gordon Smith, a Republican from Oregon, told the newspaper. Mr Bush believes "that the political processes have been overtaken by sectarian violence and that sectarian violence must be quelled so political processes can be restored," he said.

Senator Lindsey Graham, a Republican from South Carolina, who also met Mr Bush, told The New York Times that the troop increase — coming at a time when polls show that six out of ten Americans think the war is not worth fighting — was just one element of a larger change in strategy.

Mr Bush's plan is also expected to include a number of specific goals for Mr al-Maliki's government, such as bringing more Sunnis into the political process and legislation that would fairly distribute Iraqi oil revenue to all regions.

But the central goal remains that of containing the sectarian violence that is threatening overwhelm the country. Mr Bush is expected to try and characterise the troop surge as a complement to a new security strategy outlined by Mr al-Maliki in Baghdad on Saturday, the Post reported.

The most striking part of that plan is a commitment to confront the Mahdi Army, the biggest Shia militia in Baghdad recently identified by the Pentagon as the most destabilising force in Iraq's sectarian conflict. Until now Mr al-Maliki, a Shia, has been noticeably reluctant to fight the Mahdi Army, based in Baghdad's sprawling Sadr City suburbs, for fear of losing control of his government altogether.

Washington analysts quoted in US press reports said today that Mr Bush is seeking to win back the trust of the American people for his Iraq strategy and to use that support to pressure the new, Democratic-controlled Congress into releasing the funding for the troop surge.

So far the Democrats have suggested that Mr Bush should follow the recommendations of the Iraq Study Group and find an end to the war rather than escalate the fighting. But The New York Times reported today that the party was split over whether it should openly defy the White House and insist on legislation that would give Congress control over troop levels in Iraq, as happened during the Vietnam War.

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