Gen. David Petraeus has been tapped to become the next commander of U.S. Central Command, which oversees military operations from the Middle East to Central Asia and directs the wars in Iraq and Afghanistan.

Defense Secretary Robert Gates announced his decision Wednesday at a press conference in Washington, saying President Bush would send Petraeus' nomination to the Senate soon.

"I recommended him to the president because he is absolutely the best man to do the job. The conflict in Iraq and Afghanistan are very much characterized by asymmetric warfare and I don't know anyone better prepared to deal with that," Gates said of Petraeus, speaking to reporters.

Petraeus issued a statement shortly afterward.

"I am honored to be nominated for this position and to have an opportunity to continue to serve with America's soldiers, sailors, airmen, Marines, Coastguardsmen, and civilians," Petraeus said.

Gates also announced other shifts in military leadership affecting Iraq. Should the Senate confirm Gates' choices, the changes likely would not take place until late summer or early fall because of U.S. troop movements in Iraq that are planned to take place through the summer as part of the drawdown from last year's surge. Iraqi provincial elections in the early fall also are front and center on U.S. commanders' security plans, and could keep Petraeus stationed in Baghdad.

Under Gates' recommendations, taking Petraeus' position as the senior commander in Iraq would be Army Lt. Gen. Ray Odierno, who had until recently been serving as Petraeus' deputy. Odierno had been recommended to become the Army vice chief of staff, but Gates said that nomination is being withdrawn to fill the Baghdad position that would be opened by Petraeus' promotion.

Gen. Peter Chiarelli, who has served as senior military assistant to Gates, will be nominated to the Army vice chief of staff position, Gates said.

"I respectfully ask the Senate to move on them expeditiously, hopefully by Memorial Day," Gates said. Both positions will require Senate confirmation.

Senate Majority Leader Harry Reid, D-Nev., said the nominations will be a high priority, but he indicated the choices will face tough scrutiny as he criticized the administration's war policy.

Reid said challenges facing the next CentCom and Iraq commanders include "making America more secure, restoring America's power and influence in the world, fixing our costly strategy in Iraq, and articulating a more effective strategy for winning in Afghanistan and defeating Al Qaeda in Pakistan."

"Our ground forces' readiness and the battles in Afghanistan and against Al Qaeda in Pakistan have suffered as a result of the current costly Iraq strategy," Reid said in a statement issued from his office. "These challenges will require fresh, independent and creative thinking and, if directed to by a new resident, a commitment to implementing major changes in strategy.

"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."

Speaking with reporters after the announcement, Gates said he already had spoken with top Senate leaders, including Armed Services Committee Chairman Carl Levin, D-Mich., and the top Republican counterpart on the committee, Sen. John McCain, R-Ariz., as well as key Republican Sen. John Warner of Virginia. The committee would be the first to take up the nomination, and will send its recommendation to the full Senate.

"I don't really anticipate any problems," Gates said.

And it that could be the case, according to a Democratic Senate leadership aide who spoke with FOX News. The aide indicated there would be "tough questions," but likely no objections to the nomination, and the process could be done as early as July 4.

A spokeswoman for Levin said only that the chairman of the Senate Armed Services Committee was "hoping to schedule a prompt confirmation hearing." Sen. Joseph Biden, D-Del., chairman of the Senate Foreign Relations Committee, said he hopes Petraeus "does not bring an Iraq bias to his new job, at the expense of America's broader security needs."

GOP presidential hopeful John McCain, R-Ariz., said he supports both Petraeus and Odierno. He called Petraeus "one of the great generals in American history."

Petraeus would replace Navy Adm. William Fallon, who abruptly stepped down in March after a magazine reported that he was at odds with Bush over Iran policy. Fallon said the report had become a distraction.

Petraeus, 55, is widely hailed by the Bush administration and members of Congress for developing and implementing a new strategy in Iraq, including the deployment of some 30,000 additional troops, that dramatically improved security.

In making the announcement, Gates noted the importance of CentCom to the U.S. mission around the world.

"Admiral Fallon's unexpected decision to step down as commander of Central Command on March 11 created a vacancy at one of our most important combatant commands, one engaged in two wars, and on many fronts, and perhaps the most sensitive part of the world," Gates said.

FOX News' Jennifer Griffin, Trish Turner, Justin Fishel and The Associated Press contributed to this report.