(Adds details) BAGHDAD, Feb 10 (Reuters) - The new U.S. military commander in Iraq, General David Petraeus, said on Saturday Iraq was doomed to continuing violence if a crackdown on sectarian strife now under way in Baghdad failed. "The mission is doable .... The prospects for success are good. Failing that, Iraq will be doomed to continuing violence and civil strife and surely that is a prospect all must strive to avoid," he said. "The stakes are very high," he said, speaking at a ceremony at a U.S. base near Baghdad airport where he took command of 130,000 U.S. troops in the country from General George Casey . He was speaking just days after an offensive began in Baghdad that is seen as the last chance to halt the country's slide into all-out civil war. Petraeus, a veteran of two Iraq tours and a counter- insurgency expert is widely regarded as one of the U.S. Army's best commanders. He told senators in January that the situation in Iraq was "dire" but not hopeless. He has urged that 21,500 extra American troops being sent to Iraq for the campaign to be deployed as quickly as possible. Casey had been sceptical of troop increases. The offensive is expected to build up gradually over the coming weeks and months. Tens of thousands of Iraqi and American soldiers are expected to take part. Most of the extra troops being sent to Iraq by U.S. President George W. Bush will be deployed in Baghdad. Both Bush and Shi'ite Iraqi Prime Minister Nuri al-Maliki are under mounting pressure to halt Iraq's descent into chaos. More than 3,000 American soldiers and tens of thousands of Iraqis have been killed in four years of war. Petraeus led the U.S. Army's 101st Airborne Division in the 2003 U.S.-led invasion and won plaudits for working closely with local leaders to stabilise the northern city of Mosul, getting involved in everything from privatisation to local elections. He also oversaw a new U.S. military manual on fighting insurgencies that stresses understanding politics, ethics and local culture.
