SAN DIEGO — The drawdown of Marines from the former Sunni insurgent stronghold of Anbar will take time because there is still much work to be done, a top U.S. commander said Sunday on the eve of the once violent province’s transfer to Iraqi security control.

Today’s handover of Anbar, scene of some of the bloodiest battles of the Iraq war, marks a major milestone in America’s strategy of turning security responsibility over to the Iraqis so that U.S. troops can eventually go home.

“The Marine force will be smaller soon,” Marine Maj. Gen. John Kelly said. “I don’t think it will be overnight. I think it will happen incrementally.”

Kelly said he has already made his recommendation for troop cuts in the province to the top-ranking U.S. commander in Iraq, Gen. David Petraeus, who is widely expected to conclude in the coming weeks that the outlook in Iraq has improved enough to merit more troop reductions this fall.

Kelly’s comments come after the top Marine Corps general, Gen. James Conway, said last week that fewer Marines were needed in Iraq and could be shifted to other places, such as Afghanistan.

Kelly said he has seen his troop level drop in the region from 37,000 troops in February to 25,000 today. He has also has seen a 60 percent drop in Iraqi troops in the region after several battalions were sent to fight Shiite militias in the southern city of Basra and Baghdad’s Sadr City.

Kelly made clear that the U.S. military mission in Anbar was not finished. “Our job until we leave, whenever that is, is to continue training the Iraqi police, training the Iraqi army, giving them advice … and continuing to be a force for stability,” he said.