In recent days, US military commanders have delivered a bleak message about Iraq: The number of American troops there is not likely to be substantially reduced anytime soon.
Yet the current force may have been strained near the breaking point by frequent deployments to the region, say experts. That means in the months to come, the Pentagon could face increased pressure to expand the size of the active-duty Army, or rely even more heavily on call-ups of National Guard and Reserve units.
Recruiting more soldiers would take time. But any kind of action might be welcomed by those already in uniform, many of whom have served multiple tours of duty in the Middle East.
"As a matter of fairness, we should be trying to help these people," says Michael O'Hanlon, a military expert at the Brookings Institution in Washington.
Currently, about 144,000 US troops are in Iraq, said Army Maj. Gen. William Caldwell, chief US military spokesman in Iraq, at an operational briefing in Baghdad this week. There is no predetermined force level set months in advance, said General Caldwell. Instead, the numbers depend on the requirements necessary to carry out the US mission at any given point in time.
"What we've always said is that the level of troops here in the country of Iraq [is] conditions-based," said Caldwell.
Late last year, US military officials said they hoped the number of US troops on the ground could be cut to the 100,000 level by the end of 2006. But like so many other US expectations about progress in the region, that turned out to be overly optimistic.
A surge in sectarian violence, and continued insurgent activity, means that the US force in Iraq will stay at current levels through the beginning of next year, Army Gen. John Abizaid, chief of US Central Command, told a group of military reporters in Washington this week.
"We clearly did not achieve the force levels we had hoped to," said General Abizaid.
In the short run, violence against US troops may even increase in Iraq, as Al Qaeda fighters there step up activity during the Islamic holy month of Ramadan. Already, the past week has seen an increase in execution-style murders in Baghdad, according to US officials.
Meanwhile, the pace of deployments to Iraq has battered the US military, particularly the Army and Marine Corps.
Army officials would like to have a cushion of two brigades training and resting at home for every one brigade of approximately 3,500 personnel deployed overseas. But real-world conditions have meant the actual ratio is one brigade at home to one overseas.
In practical terms, this means that active-duty brigades get only one year at home in between tours of duty in Iraq or Afghanistan, as opposed to the goal of two years.
"Five years into major combat operations in Afghanistan and Iraq, our nation's armed forces are under enormous strain," concludes a recently released report on the region by the Center for Strategic and International Studies in Washington.
This strain affects more than people, according to CSIS. Army leaders now consider all nondeployed Army brigade combat teams in the United States – both active and National Guard – to be unready for operations. Equipment and personnel shortfalls may mean the US does not have the forces it needs to respond to a terrorist attack or unexpected crisis.
"National leaders need to honestly debate whether the country can continue to prosecute multiple overseas operations without increasing the size of US ground forces," says the CSIS study.
About 500,000 soldiers are currently in the Army. Plans call for it to increase to about 512,000 in the foreseeable future.
But even reaching that level may take time. Growing beyond that, if authorized, would take even longer. And the need is pressing now, note experts.
Short of obligatory national service, moves such as opening the US military to foreigners with no US ties, but who wish to move toward US residence or citizenship, might be necessary for the Army to grow in a reasonable amount of time.
"It takes a couple of years to make a meaningful increase in the size of the Army," says Mr. O'Hanlon of the Brookings Institution.
The US could send National Guard and Reserve units back to Iraq on a faster deployment schedule, but many such units have already hit legal limits that allow them to be sent overseas only two years out of every five.
Given the level of violence and the pace of training of Iraqi forces, substantial numbers of US troops may well remain in Iraq at least through the presidency of George W. Bush, and perhaps beyond.
It will be two to three years at the earliest before Iraq's regular military forces can stand on their own against Iraqi insurgents and militias, according to CSIS military expert Anthony Cordesman. It will be five years before they will be strong enough to defend against neighboring states.
"There can be no fixed time scale for US reductions," writes Mr. Cordesman in an analysis released earlier this year.
• Wire services were used in this report.