(Corrects number of U.S. troops who have died from "some 3,100" to "more than 3,200" in paragraph 7) By Andrew Gray TAMPA, Fla., March 16 (Reuters) - Adm. William Fallon took over on Friday as new U.S. commander for the region that includes the wars in Iraq and Afghanistan and said the situation in Iraq was critical. Fallon replaced Army Gen. John Abizaid at U.S. Central Command, which is responsible for the U.S. military in 27 countries. "The situation in Iraq is critical and time is of the essence," Fallon told U.S. and allied soldiers at a ceremony in an aircraft hangar at the headquarters in Tampa, Florida. He said U.S. and Iraqi forces were engaged in a security crackdown that began last month, and that the U.S. military and NATO allies also had launched a new operation to fight Taliban insurgents in Afghanistan. "Despite these challenges, we have an awful lot going for us," Fallon said. "We have vast capabilities in this nation of ours and, in concert with our allies, if we put our minds to it, there's very little that we can't accomplish." More than 3,200 U.S. troops have died since U.S.-led forces invaded Iraq in March 2003. Fallon is the first Navy officer to run Central Command, a headquarters that combines elements from all U.S. military services, since it was created in 1983. He was previously in charge of Pacific Command. Defense Secretary Robert Gates praised Fallon as "one of the best strategic thinkers in uniform today" and said Abizaid, who is retiring after running Central Command since July 2003, had enjoyed "one of the more storied military careers in recent memory". But Gates also said: "In all of these efforts, I am sure that General Abizaid would agree that not everything has gone as planned, as expected, or as hoped. This is the nature of war."
