Washington, D.C. ? Military officials said Monday that about 3,200 Marines are being told to prepare to go to Afghanistan – a move that will boost combat troop levels in time for an expected Taliban offensive this spring.

Once complete, the deployment would increase U.S. forces in Afghanistan to as much as 30,000, the highest level since the 2001 invasion after the terrorist attacks on the World Trade Center and the Pentagon.

The military began notifying the Marines and their families over the weekend, as Defense Secretary Robert Gates was expected to sign the formal deployment orders. It was not clear Monday whether the orders had been signed yet.

Commanders faced with increasing violence have said they need as many as 7,500 more troops, but Gates initially pressed for other NATO nations to fill the void.