(This is breaking on the BBC)
President Bush has authorized the marines to recall the inactive reservists (marines who have been out of the corp, not training or anything) 2,500 at a time to serve in Iraq and Afghanistan. This is not going to be popular with those marines who thought that they were done with the war, or with their families.
See below the fold for the rest of the BBC's story.
Thousands of marine reserves have already served in Iraq, but they were active reservists who train regularly.
Now inactive reservists obliged only to report one day a year may be recalled - against their will if necessary.
The Marine Corps describes the move as prudent planning, but critics will seize on the announcement as evidence the US military is overstretched in Iraq, reports the BBC's James Westhead in Washington.
The call-up, authorised by President George W Bush, will affect members of the Individual Ready Reserve (IRR).
Under a general contract, a marine serves four years on active duty, and then a further four years in the reserve forces. For this final four years, they can either elect to join the regular reserves - where they are paid and train regularly - or choose to join the IRR.
Col Guy Stratton, head of the Corps' manpower mobilisation section, told the news agency Reuters that in recent times fewer marines had been choosing to volunteer for the active reserves.
No expiry date
The Marine Corps have now been given permission to recall up to 2,500 marines for duty at a time.
But the authorisation is open-ended and will only expire once the so-called "Global War on Terror" (GWOT) - a war whose parameters are largely undefined - has ended, so many thousands could eventually end up serving.
Reservists could be required to serve up to 24 months, but will more likely serve between 12 and 18 months, said Col Stratton.
Our correspondent says the US army has already recalled around 10,000 inactive reserve soldiers.
But he says the smaller marine force plays a key role in Iraq, shouldering a significant portion of the fighting. They also serve in some of the most dangerous parts of the country.