National Guard troops played a leading role responding to Hurricane Katrina's destruction along the U.S. Gulf Coast on Tuesday, but thousands more who might have been part of the effort are deployed in Iraq.

About 7,500 National Guard soldiers and airmen have been mobilized by state governors for disaster relief in Louisiana, Mississippi, Alabama and Florida, Pentagon spokesman Bryan Whitman said.

They were assisting in law enforcement, helping at shelters and in medical efforts, removing debris, providing power generation and other missions.

The Pentagon has sent about 40 percent of Mississippi's National Guard force to Iraq and 35 percent of Louisiana's -- a combined total of about 6,000 troops. But officials maintained this had not hurt the relief effort in those states, hardest hit by the hurricane.

The Army National Guard was formed as a part-time force, with its members living civilian lives while doing periodic military training. But the Pentagon has relied heavily on these troops in combat roles in Iraq.

Unlike soldiers in the part-time Army Reserve, made up of federal troops, those in the National Guard serve under the control of state governors usually for roles like disaster relief in their home states. They can be summoned to active-duty Army service in times of national need.

Some state governors have worried that the Pentagon's deployment of so many Guard troops has eroded their states' abilities to respond to disasters like wildfires and hurricanes. The Pentagon has promised never to deploy more than half of a state's guard force at any given time.

"It certainly means that they (the states) don't have the level of personnel that they might desire to handle some of these situations. They're doing with the minimum, not what might be optimal," said Cato Institute defense analyst Ted Carpenter.

The Pentagon said 78,000 of the roughly 440,000 National Guard troops nationwide are deployed overseas. Some troops and families have complained about the overseas combat duty and the Army National Guard is poised to miss its recruiting goals for a third straight year.

Two other states affected by the hurricane also have large numbers of their National Guard troops overseas; 23 percent of Alabama's and 26 percent of Florida's are deployed.

"None of the states impacted are stretched thin at all," said Jack Harrison, a National Guard Bureau spokesman at the Pentagon, noting there are about 31,500 guardsmen either activated or available to be activated in the four states.

Lt. Col. Ellen Krenke, a Pentagon spokeswoman, said an interstate agreement allows states voluntarily to provide personnel and equipment to neighboring states in emergencies.

For example, the Arkansas National Guard has activated 350 troops to assist in Mississippi.

A number of Western states that rely on the National Guard to fight forest fires and handle other disasters have expressed concern about the impact of having a large number of those troops in Iraq.

Montana Gov. Brian Schweitzer, a Democrat, has criticized the Bush administration's reliance on the National Guard, saying 44 percent of his state's guard was mobilized in Iraq, far above the 21 percent national average.

"The state of Montana does not have that many assets outside the National Guard," he said earlier this month.