Under fire for the unpopular war in Iraq, President George W Bush [Images] has announced a gradual pullout of US troops from the country but rejected calls for a full withdrawal, arguing that abandoning its fledgling ally will embolden extremists and help the 'destructive' ambitions of Iran.

Claiming success of his 'surge' policy in reducing violence in the strife-torn country, Bush said he will pull out some 21,500 soldiers by July next year, which will leave around 1.3 lakh US troops in Iraq, roughly the same number just before the beginning of the increase in troop deployment last December.

'The principle guiding my decisions on troop levels in Iraq is: return on success. The more successful we are, the more American troops can return home,' he said in a televised speech to the nation on Thursday night.

Based on the advise of his top commander in Iraq, Bush said around 5,700 troops are expected to be withdrawn by Christmas.

'And by July, we will be able to reduce our troop levels in Iraq from 20 combat brigades to 15,' he said.
 
'Because of the success, General (David) Petraeus believes we have now reached the point where we can maintain our security gains with fewer American forces.'

Facing pressure from Democrat lawmakers who are demanding a complete withdrawal of troops, Bush warned of the implications of leaving Iraq before achieving complete success.

He said a 'free Iraq' was critical for security of the US, to deny a free run to extremists and to counter the ambitions of Iran.

'A free Iraq will counter the destructive ambitions of Iran. A free Iraq will marginalise extremists, unleash the talent of its people, and be an anchor of stability in the region... A free Iraq will be our partner in the fight against terror, and that will make us safer here at home,' Bush said.

If we were to be driven out of Iraq, extremists of all strains will be emboldened. Al Qaeda [Images] could gain new recruits and new sanctuaries,' Bush said, adding that Iran will be the chief beneficiary from the chaos that emerges.