The commander of US forces in the Middle East, Admiral William Fallon, said on Tuesday that he is stepping down because reports that he differed with President George W Bush over Iran had become "a distraction."
Defense Secretary Robert Gates announced he had accepted Fallon's resignation "with reluctance and regret," saying there was a "misperception" that the admiral was at odds with the administration over Iran.
In a statement, Bush praised the admiral for his more than 40 years of service but made no mention of an article in Esquire magazine that prompted Fallon to step down.
Fallon "served this country with honor, determination and commitment," Bush said.
But the sudden departure of the head of the US Central Command drew an avalanche of criticism from top Democrats who suggested that he had been forced out because of his candor.
Senate Majority Leader Harry Reid called it "yet another example that independence and the frank, open airing of experts' views are not welcomed in this administration."
Democratic presidential candidate Hillary Clinton in a statement described Fallon as a "voice of reason in an administration which has used inflammatory rhetoric against Iran," and urged the Bush administration to pursue diplomacy with Tehran instead of conflict.
"Admiral Fallon's resignation should not be used as an excuse to ratchet up tensions with Iran," the New York senator said.
Gates said there were no significant differences between Fallon's views on Iran, which has defied global calls to rein in its suspect nuclear program, and those of the administration.
Asked about Esquire's contention that Fallon's removal would signal the United States was preparing to go to war with Iran, Gates said: "Well, that's just ridiculous."
In an admiring profile of the admiral, Esquire writer Thomas Barnett portrayed Fallon as "The Man Between War and Peace," crediting him with calming tensions with Iran last year while bucking a White House move toward war.
"Well-placed observers now say that it will come as no surprise if Fallon is relieved of his command before his time is up next spring, maybe as early as this summer, in favor of a commander the White House considers to be more pliable," said the article.
"If that were to happen, it may well mean that the president and vice president intend to take military action against Iran before the end of this year and don't want a commander standing in their way."
Fallon also drew media attention in November when Bush was stepping up his rhetoric against Iran, publicly warning in an interview with the Financial Times that the drumbeat of press speculation about US military options was not helpful.
In his statement, Fallon said: "Recent press reports suggesting a disconnect between my views and the president's policy objectives have become a distraction at a critical time and hamper efforts in the Centcom region."
"And although I don't believe there have ever been any differences about the objectives of our policy in the Central Command area of responsibility, the simple perception that there is makes it difficult for me to effectively serve America's interests there," he said.
Moments later, Gates told a hastily convened news conference at the Pentagon: "I have approved Admiral Fallon's request to retire with reluctance and regret."
He said Fallon made the decision to step down "entirely on his own."
"I believe it was the right thing to do even though I do not believe there are significant differences between his views and the administration's views," he said.
Army Lieutenant General Martin Dempsey, Fallon's number two at the US Central Command, was named to replace the admiral on an acting basis when he leaves at the end of the month.
Fallon's departure comes just as the Pentagon was preparing to make recommendations on the pace and scope of a US troop drawdown from Iraq. He was supposed to give an assessment from his perch as the regional commander.
Gates said the Central Command evaluation will be completed before Fallon leaves his post, "so it will represent his views."
A former fighter pilot during the Vietnam War, Fallon came to the Central Command after serving as commander of US forces in the Pacific, where he focused on improving military relations with China.
His reputation as a strategic thinker who was also adept at diplomacy made him Gates's choice to lead the US military in an area where it was embroiled in two conflicts and faced a growing challenge from Iran.