If confirmed by the senate, Petraeus would replace Navy Admiral William Fallon, who abruptly stepped down in March after a magazine reported that he was at odds with Geoge Bush, the US president, over the administration's policy towards Iran.
 
Fallon said the report, while untrue, was a "distraction".
 
Owen Fay, Al Jazeera's correspondent in Baghdad, said that General Petraeus was "known as Bush's man and is very much a creature of this White House".
 
Unconventional conflicts
 
Petraeus oversaw the so-called US troop
"surge" in Iraq [GALLO/GETTY]
 
Asked if moving Petraeus from the Iraq command could disrupt US forces there, Gates said that by waiting until later this year he hoped to "ensure plenty of time to prepare for a good handoff".

He said it also would help that Odierno has had experience as "Petraeus' right-hand man" over the last year.

At a hastily arranged Pentagon news conference, Gates said the wars in Iraq and Afghanistan, as well as other challenges in the Central Command area of responsibility, demand knowledge of how to lead counterinsurgencies as well as other unconventional conflicts.

"I don't know anybody in the US military better qualified to lead that effort," he said, referring to Petraeus.

He also denied that the nomination of Petraeus would mean a more hardened stance by Central Command towards Iran than under Fallon, who had emphasised a more conciliatory and diplomatic stance on Tehran's nuclear programme.

"It is a hard position because what the Iranians are doing was killing American servicemen, and inside Iraq. And so I don't think that there is any difference among them on that issue whatsoever," Gates said.

General Petraeus, who oversaw and reported to US Congress on last year's so-called troop "surge" in Iraq, testified earlier this month to what he called Iran's "destructive" role in allegedly arming Iraqi Shia militia groups.

"Unchecked, the special groups pose the greatest long-term
threat to the viability of a democratic Iraq," he told the Senate
Armed Services Committee.

However, military strategist Mark Perry told Al Jazeera that neither Gates nor Petraeus favour conflict with Iran.

He said that Petraeus knows the vulnerability of US troops in Iraq more than anyone else in the US military.