President Bush will make a televised address to the American nation on Wednesday night in which he will finally unveil his new strategy on Iraq.

After overhauling his military and diplomatic teams, Mr Bush is expected to announce the 9pm (0200 GMT) address to announce an increase in US troop numbers in Iraq by 20,000.

His plan is largely opposed on Capitol Hill and among the American public, who say it is time to end the occupation of Iraq not to send in more troops.

The timing of the televised address was announced at the same time as Mr Bush's formal nomination of Zalmay Khalilzad to the post of the new US ambassador to the United Nations.

Mr Khalilzad will move from his current position as UN ambassador to Iraq, to replace John Bolton, who stepped down last year after failing to win Senate approval for his nomination.

Mr Bush will also nominate Ryan Crocker, currently the US ambassador to Pakistan, to fill the Baghdad post, the White House announced today.

The reshuffle is part of a broad mission by Mr Bush to surround himself, both in Washington and on the ground in Iraq, with officials who support increasing troop numbers.

His advocates argue that more US forces are needed to stabilise restive Baghdad, in what they call a "surge" option.

However, critics of Mr Bush have faulted his refusal that to admit the invasion was a mistake and for now opting to deepen the invasion to try and avoid a sectarian civil war.

Last week Harry Reid, Senate Majority Leader, and Nancy Pelosi, Leader of the House, wrote to Mr Bush to say that "we do not believe that adding more US combat troops contributes to success".

Tony Snow, White House press secretary, said today that Mr Bush "understands there is a lot of public anxiety" about the war.

On the other hand, he said that Americans "don't want another September 11" terrorist attack, and that it is wiser to confront terrorists overseas in Iraq rather than in the United States.

Mr Bush shows little sign of bending to his critics, apparently believing history will vindicate him for a war that has killed more than 3,000 US soldiers and tens of thousands of Iraqis.

He has already dismissed many of the main recommendations of the bipartisan Iraq Study Group, whose report last month called for a pullback of most combat forces by early 2008.

In order to fulfil his plan Mr Bush will rely heavily on extending tours in Iraq, and remobilising reserves, because the US Army is stretched so thin.

He is also expected to send two additional army brigades, or roughly 7,000 soldiers, to Baghdad, and two Marine battalions, about 1,500 troops, to western Anbar Province, the heart of the Sunni insurgency.

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