By Suzanne Malveaux and Dan Lothian, CNN White House Correspondents

Washington (CNN) -- It's still unclear whether President Obama had made up his mind before sitting down Wednesday with Gen. Stanley McChrystal, but CNN has learned that during their one-on-one meeting, Obama gave the general a chance to defend himself.

"The president asked him about the article," said a senior administration official, referring to a Rolling Stone magazine article containing comments from McChrystal and his staff that appear to mock top civilian officials, including the vice president.

"He [McChrystal] tried to explain the situation," the official said.

That senior administration official, who briefed reporters, gave this backstory:

Once Obama accepted McChrystal's resignation, he wasted no time finding his replacement. After McChrystal walked out of the White House following his 30 minute face-to-face meeting with the president, the president immediately huddled with a team of advisors to decide who would replace McChrystal.

That group included Vice President Joe Biden, Defense Secretary Robert Gates, Joint Chiefs Chairman Adm. Mike Mullen, National Security Advisor Jim Jones and Chief of Staff Rahm Emanuel. For 45 minutes, they mulled over the president's options.

The White House earlier had asked for a list of possible replacements for McChrystal in the event the president replaced him. Ge

The president chose Petraeus. There is a continuity -- Petraeus is familiar with all the players in the region and he is familiar to NATO partners.

Then Obama called Petraeus, who was already in the White House Situation Room, into the Oval Office to ask him to take over the mission in Afghanistan. The meeting lasted for 40 minutes, and Petraeus agreed.

The senior administration official said despite the fact that Petraeus was asked to give up Central Command, he did not consider it a demotion. Obama acknowledged the move was not "the normal course" for a top general to go from being in charge of Central Command to taking command in Afghanistan. The president also acknowledged it was "a sacrifice for Petraeus."

The commander in chief then went to the Situation Room, where his national security team was waiting. The senior administration official described the president as "stern" as he walked the team through his decision.

The official said the president told everyone "we need to remember why we're doing this."

Obama went on to explain that it was understandable to have disagreements or tensions within his security team, but when those disagreements turned petty, that did not serve the men and women fighting for the mission.

The president expressed "regret" and "sorrow", saying that, "this was a sad day," the senior administration official said. Then Obama wrapped up the meeting, and called Afghanistan's President Hamid Karzai to explain his decision. McChrystal and Karzai had been close, according to administration and Pentagon officials.

The president then went to the Rose Garden to face the cameras and announce his decision to the American people.

Since then, according to White House spokesman Tommy Vietor, Obama has talked to British Prime Minister David Cameron, House Speaker Nancy Pelosi, and Sens. Harry Reid, Carl Levin, and John McCain. He is urging the Senate to follow his lead and to quickly confirm his nominee.

n. David Petraeus, head of U.S. Central Command, was one of those considered.