WASHINGTON President Barack Obama will soon decide how many troops to send to Afghanistan as part of his first major deployment of forces overseas as commander in chief of the U.S. military.
The new deployments are seen as the first stage in an expected build-up from the present force of 37,000 to about 60,000. Here are is a look at how the force is likely to grow.
Obama has been expected for weeks to announce the deployment of as many as three combat units comprising up to 17,000 troops; top Pentagon officials have said they envision two of the units arriving in Afghanistan by the end of spring and a third during the summer.
U.S. military planners have been considering sending two Army brigade combat teams, each with about 3,500 soldiers, and a larger Marine task force of a number expected to approach 10,000 troops.
The Pentagon is already sending about 2,200 support troops known as enablers and an Army combat aviation brigade of 2,800 soldiers, in addition to an Army combat brigade of 3,800 soldiers that deployed last month in eastern Afghanistan.
The expected U.S. build-up would increase the total number of Western forces, including troops from other NATO countries, to around 100,000 troops.
In recent days, Pentagon officials including Defence Secretary Robert Gates have suggested the combat deployment could take place in stages beginning with a force as small as a single brigade.
Officials say the Obama administration may hold back the main deployment until it completes a strategic review in time for a NATO summit in April, but at least one brigade may have to be ordered to Afghanistan before the review is finished.
That is because of the danger of a spike in violence this spring when warm weather unclogs mountain passes and allows freer movement to the Taliban and other militant groups.
Most of the extra forces would likely be sent to south Afghanistan, where the top U.S. and NATO commander in the country, General David McKiernan, says the shortage is most acute and the Taliban's power has grown with the aid of illicit opium proceeds.
The troops' initial mission is expected to focus on reversing a deterioration in security caused by growing Taliban influence. Analysts say that will probably involve securing roads against bombs and other roadside attacks.
Extra troops will also allow commanders to hold onto territory that has been cleared of Taliban influence so that development can begin to take hold, officials say.
Ultimately, Pentagon officials say the extra forces are a stop-gap measure until the Afghan National Army can take over security operations. A U.S.-backed plan calls for increasing the Afghan military from around 80,000 troops to 134,000 but the Pentagon has said even that may not be enough.
(Reporting by David Morgan; editing by David Storey)