President George W Bush is to nominate current US Ambassador to Iraq Zalmay Khalilzad as new US envoy to the UN, it has been confirmed.

Mr Khalilzad will succeed John Bolton, who stepped down last year after the Democrats refused to back him.

This is one of several changes made by Mr Bush in the run-up to the announcement of a new Iraq policy on Wednesday (0200 GMT on Thursday).

Reports suggest he will commit to sending in thousands more soldiers.

Mr Khalilzad, 55, has worked under two previous Republican presidents - George Bush Snr and Ronald Reagan.

If his nomination is confirmed by senators, Mr Khalilzad will become the first Muslim to become US envoy to the UN.

The Afghan-born diplomat took over his Iraq role in mid-2005 after spending 18 months as ambassador to Afghanistan.

His expected appointment at the UN comes as President Bush prepares to announce a new strategy for Iraq.

White House officials confirmed the president would be addressing the nation on Wednesday on plans for "a way forward in Iraq and the global war on terror".

Mr Bush is expected to make a number of key changes in the US military leadership as part of his fresh strategy.

There will be a new head of US Central Command and a new ground commander in Iraq, officials have said.

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Zalmay Khalilzad