WASHINGTON, (Reuters) – President Barack Obama  fired his top Afghanistan commander yesterday over  inflammatory comments that enraged the White House, and vowed  not to let the military shake-up undermine the U.S. war  effort.

In an extraordinary turn of events, Obama called General  Stanley McChrystal on the carpet at the White House, relieved  him of command and replaced him with his boss, General David  Petraeus, architect of the Iraq war turnaround. Obama had summoned McChrystal from Afghanistan to answer  for remarks he and his aides made in an explosive Rolling Stone  magazine article that disparaged the president and other  civilian leaders.

“The conduct represented in the recently published article  does not meet the standard that should be set by a commanding  general,” Obama said bluntly in the White House Rose Garden as  he announced McChrystal’s dismissal.

“It undermines the civilian control of the military that is  at the core of our democratic system. And it erodes the trust  that’s necessary for our team to work together to achieve our  objectives in Afghanistan,” he said.

The situation posed a dilemma for Obama. If McChrystal had  kept his job, the president could have been seen as tolerating  insubordination. By firing him, Obama opted instead for the  risk involved in shaking up the chain of command at a perilous  moment in the unpopular nine-year-old war.

Obama said McChrystal’s dismissal was needed to safeguard  the unity of the war effort but insisted the switch in generals  was a “change in personnel but it is not a change in policy.”

There have been increasing doubts among U.S. lawmakers  about Obama’s six-month-old troop buildup strategy against a  resurgent Taliban, and some critics are skeptical of Obama’s  pledge to start bringing U.S. forces home by July 2011.

Seeking to underscore the continuity of command and counter  any concerns about a disruption in war leadership, Obama had  Petraeus by his side for the announcement.

Petraeus, as commander of U.S. forces in Iraq, was widely  credited with turning the tide when sectarian violence there  verged on civil war. He has a strong following on Capitol Hill  and swift Senate confirmation is expected.

Afghan President Hamid Karzai, who has a close bond with  McChrystal and had hoped he would stay on, respected Obama’s  decision to dismiss him, a spokesman said.

Obama spoke to Karzai and British Prime Minister David  Cameron, a key ally in Afghanistan, about the change. The episode evoked memories of military-civilian tensions  when President Harry Truman summoned General Douglas MacArthur  for a dressing-down and stripped him of his Far East command in  1951 for flouting U.S. policy and openly advocating expansion  of the Korean conflict to China.

McChrystal, the U.S. and NATO commander in Afghanistan and  an architect of Obama’s war strategy, entered the White House  through a side door for his encounter with Obama, who accepted  his letter of resignation during a 30-minute meeting.

Underscoring Obama’s displeasure over the McChrystal  incident, he then delivered a “stern” lecture to his national  security team, ordering them to stop petty bickering and forge  unity, a senior administration official.

Aides had described Obama as furious about McChrystal’s  contemptuous remarks in the article, but he said in his Rose  Garden appearance he was not acting out of a feeling of  personal insult.

With his career on the line, the 55-year-old general had  apologized on Tuesday, calling it a “mistake reflecting poor  judgment.”

As Obama was speaking, McChrystal released a terse  statement saying he had resigned out of “a desire to see the  mission succeed.”

Lieutenant-General David Rodriguez, McChrystal’s No. 2, was  named acting commander of U.S. forces in Afghanistan, and  British Lieutenant-General Nick Parker will serve as acting  head of NATO forces in Afghanistan until Petraeus takes over,  U.S. officials said.