BAGHDAD — The U.S. military announced Tuesday that five soldiers and a sailor had been killed a day earlier, making 2007 the deadliest year for U.S. troops since the start of the war in Iraq.

The record death toll of at least 853 U.S. military personnel killed this year underscores the high cost of the U.S. troop increase, launched in February, which has begun to drive down the sectarian violence that once gripped much of the country.

"The strategy was to interject our soldiers between the Iraqi citizens and the terrorists, insurgents and militias," said Lt. Col. Douglas Ollivant, chief of plans for U.S. forces in Baghdad. "A regrettable consequence of that is your casualties go up."