WASHINGTON — Iraq’s armed forces are being primed to take near-total control of the country within 18 months, America’s senior commander in Baghdad said yesterday.

The comments by one of America’s most senior officers, General George Casey, offered a rare glimpse into the American military’s timetable for leaving Iraq.

“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,” General Casey said in Baghdad.

The handover will not necessarily bring immediate major reductions in American troop levels, which have been forced upward in recent months by the insurgency. But it would be likely to take many American units off the streets and into heavily fortified bases.

The Americans say that while Iraqi front-line units have been created, the new army lacks troops for critical tasks including logistics and intelligence. Thirteen Iraqi soldiers were “executed” by guerrillas on Monday during fierce clashes in Diwaniya after they ran out of bullets.

Previous optimism about cutting American troop levels in Iraq has proved ill-founded. Last year, the Washington Post reported that troop numbers would fall below 100,000 by the end of this year, according to a “moderately optimistic” assessment of events.

Numbers fell early in the year. But troop levels later returned to 136,000, in part because Iraqi forces were unable to deal with insurgents.

Violence in Baghdad was increasing greatly until American reinforcements arrived this month.

Britain has reduced its troop levels to 7,000, which remain higher than planned. The British army had wanted to bring numbers down to 3,500 this year but that has been postponed until next year.

General Casey said the first part of the three-stage handover plan — training and equipping Iraqis — was complete.

The second, requiring them to lead military operations with coalition support, was “75% complete.” As part of the plan, General Casey will hand operational control of Iraq’s armed forces to the government of Prime Minister al-Maliki next month.

The final stage, in which coalition forces withdraw to their heavily defended bases leaving the Iraqis in sole control, is not yet under way.