Baghdad, Iraq ? The top U.S. commander in Iraq expressed optimism Wednesday that Iraqi forces are making enough progress to provide their own security within 18 months. But violence showed no sign of abating, with 66 people killed nationwide, including 24 in a Baghdad market bombing.

The U.S. military also reported Wednesday that a Marine was killed in action the day before in the volatile Anbar province.

Gen. George Casey said Iraqi troops were on course to take over security control from U.S.-led coalition forces, a move that would bring the foreign forces a step closer to withdrawal from the country.

“I don’t have a date, but I can see over the next 12 to 18 months, the Iraqi security forces progressing to a point where they can take on the security responsibilities for the country, with very little coalition support,” he said.

That takeover would not mean U.S. troops leaving immediately. It is part of a U.S. military plan to hand over responsibilities, move into large bases and provide support while Iraqis take the lead. A U.S. drawdown would start after that occurred.

Casey’s comments came even as violence surged in the capital and elsewhere, undercutting claims by U.S. and Iraqi officials that a Baghdad security crackdown has lowered Sunni-Shiite killings, which had risen in June and July.

On Monday, U.S. military spokesman Maj. Gen. William B. Caldwell said the murder rate in Baghdad had fallen by 46 percent from July to August and “we are actually seeing progress out there.” That figure could not be independently confirmed.

U.S. officials attributed the fall in sectarian killings to a major security crackdown launched Aug. 7. About 8,000 U.S. troops and 3,000 Iraqi soldiers were sent to the capital to search homes systematically and patrol the streets.

Similar operations have curbed violence for limited periods of time in the past, only to have killings flare again once American forces left.

A bomb struck one of Baghdad’s largest market areas, where food, clothing and household goods are sold, killing at least 24 people and wounding 35, police said.

In Hillah, 60 miles south of the capital, a man posing as a potential army cadet left a bomb-laden bicycle outside a recruiting center, killing 12 people, police said. Insurgents often target Iraqi army and police recruits as a way to discourage volunteers.

Elsewhere, a roadside bomb killed a family of five in Buhriz, 35 miles north of the capital, when a roadside bomb struck their car. Bombings and shootings elsewhere in the country killed another 25 people, according to police.

Ten bodies also were found – five dumped in Suwayrah, 25 miles south of Baghdad, and the others in the capital.

Still, Casey said he was optimistic about security in Iraq and said an operation to crack down on violence in the capital was producing results – although more needed to be done.

“I’m pleased with the progress to date, but we have a long way to go,” Casey said. “And we’re not going to let up until we get where we’re going and bring security to the neighborhoods of Baghdad.”