Washington ? President Bush is promoting his top Iraq commander, Army Gen. David Petraeus, and replacing him with the general’s recent deputy, keeping the U.S. on its war course and handing the next president a pair of combat-tested commanders who have relentlessly defended Bush’s strategies.

Bush will nominate Petraeus to replace Navy Adm. William J. Fallon as chief of U.S. Central Command, Defense Secretary Robert Gates announced Wednesday. The command’s area of responsibility features some of the most vexing military and foreign policy problems facing this administration and its successor – including Iran, Pakistan, Lebanon, parts of Africa and Afghanistan in addition to Iraq.

Fallon resigned last month, saying news reports that he was at odds with the White House over Iran policy had become a distraction. He was the first Navy officer to lead Central Command; the Petraeus choice represents a return to the more common practice of making it an Army slot.

Petraeus would be succeeded at a pivotal time in Baghdad by Army Lt. Gen. Ray Odierno, who was the No. 2 commander in Iraq for 15 months. He has been credited by many with deftly managing security gains that Petraeus told Congress this month have opened a pathway for potential political progress in the country.

Gates said he hoped the Senate would act on both nominations by next month and expected Petraeus to switch to the Central Command job, which is based in Tampa, Fla., by late summer or early fall.

That is the point at which Petraeus is likely to make an initial recommendation to Gates and to Bush on whether conditions in Iraq are stable enough to permit a further reduction in U.S. troop levels.

The United States has about 160,000 troops in Iraq and about 28,000 in Afghanistan. The strain of those wars has taken a heavy toll on U.S. ground forces.

Among the politically sensitive questions Petraeus would face as head of Central Command is whether the military focus on Iraq is limiting what U.S. and allied forces can accomplish in Afghanistan. And he would be pressed on the matter of using military force against Iran.

The next president taking office in January would not be compelled to keep either Petraeus or Odierno, but normally the lineup of senior commanders – as well as the chairman of the Joint Chiefs of Staff – is not changed with administrations.

“There is no precedent in U.S. tradition for a new president changing these kinds of officers,” said Stephen Biddle, a senior fellow at the Council on Foreign Relations and an occasional adviser to Petraeus. “For an incoming president to change them (in 2009) would be a real statement.”

Many Republicans, including all-but-certain presidential nominee John McCain, are enthusiastic Petraeus supporters. Democrats on Capitol Hill are not expected to oppose either Petraeus or Odierno, but they are likely to raise tough questions during confirmation hearings.

Senate Majority Leader Harry Reid noted after Gates’ announcement that any war commander must be committed to “implementing major changes in strategy” if directed to do so by a new president.

“The Senate will carefully examine these nominations, and I will be looking for credible assurances of a strong commitment to implementing a more effective national security strategy,” said Reid, D-Nev.

At a Pentagon news conference, Gates said he did not foresee that the new lineup at Central Command and in Iraq would mean any changes in the way the U.S. is approaching the issue of Iranian influence in Iraq. Petraeus and Odierno have both accused Iran of aiding rebels opposing U.S. troops.

“It’s my belief that General Odierno and General Petraeus and Admiral Fallon were all in exactly the same position when it came to their views of Iranian interference inside Iraq,” Gates said. “And it is a hard position. Because what the Iranians are doing is killing American service men and women inside Iraq.”

Petraeus will face broader aspects of the Iran issue if he is confirmed as Fallon’s replacement. A number of U.S. officials, including Adm. Michael Mullen, chairman of the Joint Chiefs of Staff, have asserted that Iran also is supplying arms or otherwise supporting the Taliban rebels in Afghanistan.