WASHINGTON (Reuters) - The Bush administration picked Gen. David Petraeus, its top commander in Iraq, on Wednesday to take charge of operations across the Middle East and chose his former No. 2 to take over in Baghdad.

The decision to elevate both Petraeus and Lt. Gen. Raymond Odierno, who together implemented a new military strategy that drove violence down in Iraq, signals that Washington does not plan any major changes in its approach to that war.

It also shows the Pentagon’s desire to apply Petraeus’ experience in fighting insurgencies to Afghanistan, where violence has soared as the Taliban and al Qaeda regrouped.

U.S. Defense Secretary Robert Gates called Petraeus the most qualified general to lead the U.S. Central Command, manage counterinsurgency operations in both wars and face threats including Islamist extremism throughout the region.

“I don’t know anybody in the United States military better qualified to lead that effort,” Gates said.

President George W. Bush has approved both recommendations and will send the nominations to the U.S. Senate, Gates said.

The White House asked the Senate to act on the nominations quickly, by the end of May, but Gates said he did not expect the changes to take effect until “late summer or early fall.”

If confirmed by the Senate, Petraeus will replace former Adm. William Fallon, who resigned after a reported break with the Bush administration over Iran policy. His nomination also puts an Army general, rather than a Navy admiral, back in charge of the two ground wars.

IRAN, PAKISTAN PORTFOLIO

Central Command is considered the toughest regional military command to lead.

There, Petraeus will oversee U.S. operations in a region that includes Iran, Pakistan and 25 other countries as well as international waters that are both strategically and economically significant, such as the Gulf.

It also includes the Strait of Hormuz, arguably the most prominent choke point in the global crude oil trade, handling more than a third of total water-borne crude oil shipments.

Petraeus will face competing requirements for troops and equipment in Iraq and Afghanistan. He also will be responsible for supporting Pakistan’s counterterrorism efforts and managing rising tensions with Iran.

Army Gen. David Petraeus, commanding general of Multi-National Force-Iraq, answers a question during a meeting with members of the Department of Defense press pool travelling with Secretary of Defense Robert M. Gates in Baghdad, in this December 6, 2007 file picture. REUTERS/Haraz N. Ghanbari/Pool

“Each is at least as important to America’s long-term security as the Iraq conflict, yet the United States does not have as direct a role or as much influence in Iran or Pakistan as it’s had and still has in Iraq,” said Michael O’Hanlon, an analyst at the Brookings Institution in Washington.

Both Petraeus and Odierno have spoken out strongly on Iran, saying it is the most serious long-term threat to Iraq.

Some Democrats said they worry Petraeus will focus too heavily on Iraq as head of Central Command, neglecting other national security threats.

“Congress must ensure that Gen. Petraeus does not bring an Iraq bias to his new job, at the expense of America’s broader security needs,” said Sen. Joseph Biden, a Delaware Democrat and chairman of the Senate committee on foreign relations.

Gates said he spoke with senior senators and did not expect problems with the nominations.

COUNTERINSURGENCY APPROACH

When Petraeus arrived in Iraq in February 2007, the country was on the verge of all-out civil war between majority Shi’ites and minority Sunni Arabs.

Petraeus implemented a new strategy, ordering his troops to leave the relative safety of big bases and set up smaller outposts with Iraqi forces to better protect the population.

His strategy, coupled with the addition of about 30,000 more U.S. troops, was widely credited with driving violence and casualties down throughout the country.

That strategy created enough relative calm for Iraqi lawmakers to advance legislation seen by Washington as critical for long-term stability, although U.S. officials still see the political progress as insufficient.

“The course, certainly that Gen. Petraeus has set, has been a successful course. So, frankly, I think staying that course is not a bad idea,” Gates said.

Petraeus’ counterinsurgency approach could have the most impact on Afghanistan, where a NATO-led force has struggled to hold on to security gains against the Taliban and al Qaeda. The United States plans to add troops to that war zone.

Gates noted that the U.S. military has had success in the area of Afghanistan it controls -- the eastern region.

“The question is, how do we do a better job with our allies” in Afghanistan’s restive south, Gates said.