WASHINGTON, Jan. 4 (Xinhua) -- As the White House mulls a surge in U.S. troops in Iraq, a number of military experts warned that this could place an almost "fatal" strain on an already stressed force, Fox News reported on Thursday.

    They are also worried that the plan could reduce recruiting standards in a push to meet numerical goals, according to the report.

    U.S. President George W. Bush is expected to offer his strategy for Iraq sometime before the State of the Union address, which is scheduled for Jan. 23.

    The president has hinted that he may want to increase the number of U.S. forces around Baghdad or embedded with Iraqi soldiers.

    However, some military experts said increasing troop levels in Baghdad would mean keeping existing brigades there longer, bringing U.S. troops in from other areas of Iraq and accelerating deployments from home.

    If any of these were to be done long-term, rules for mobilizing the reserves and National Guard would have to be changed so they could be redeployed more often.

    "Surge? Yes, we can," said retired Army Col. Douglas MacGregor,a veteran who led armored cavalry in Operation Desert Storm.

    However, "it will break the force, which in my estimation is broken already. It will leave you with no strategic reserves," he said.

    Retired Army Col. David Hunt said the prospect of assigning soldiers and Marines in Iraq for longer tours of duty is cause for worry.

    The size of the active duty U.S. military will no doubt have to grow to keep up, the experts said.

    The president announced in December that he would ask Congress to expand the size of the Army and Marine Corps, but did not say by how much.

    Currently, about 507,000 soldiers are on active duty in the U.S Army and 180,000 Marines are in active service.

    The U.S. military has 520,000 National Guard and reservists. All but 90,000 of these part-time soldiers have been mobilized at least once since the Sept. 11 terror attacks, and current guidelines say they cannot be redeployed yet.

    Meanwhile, estimates are that the U.S. Army will have to expand to as many as 600,000 active duty soldiers to fight a protracted global "War on Terror."

    "I think you have to increase the size of the military before you can think of increasing the troop levels in Iraq," said retired Marine Col. Gary Anderson, a fellow at the Potomac Institute for Policy Studies, a military think tank.

    If not, "I think it will break both the Guard and the reserves and really hurt the active duty military. We just don't have the troops to try and do everything," he said.