WASHINGTON - The wars in Iraq and Afghanistan are stretching the U.S. Marine Corps, forcing the service to take extraordinary measures to bolster both manpower and equipment.

On Tuesday, the Marines announced plans to recall as many as 2,500 inactive reservists to involuntary active-duty service to meet manpower needs, the first such call-up since nearly 2,700 Marines were recalled to active-duty before U.S. forces invaded Iraq in 2003.

The announcement coincided with a report to be issued today by two military experts who say that the Marines are having to borrow equipment from non-deployed units and pre-positioned stockpiles to replace tanks, trucks, armored vehicles and other hardware worn out by more than three years of combat duty in Iraq.

The two events are the latest signs that the U.S. military is having difficulty maintaining its combat readiness with the Iraq war well into its fourth year.

A Marines spokeswoman denied that the Marines are having difficulty finding recruits or volunteers for war-zone duty. Instead, Maj. Gabrielle Chapin said the service is looking to deepen the availability of Marines with specific training. "What we do need is a pool of very specific skill sets to fill critical job specialties," she said.

Yet the call-up is a rare one for the smallest of the country's four military services, which has always prided itself on its recruitment and retention record. Less than 180,000 Marines serve on active duty, but the Corps has consistently met or exceeded its recruiting and re-enlistment goals for years, even as the wars in Afghanistan and Iraq drag on.

Those expected to receive involuntary activation notices include infantry and other combat specialties, communications and intelligence specialists, combat engineers and military police, the Marines said. Marines in their first and last years of inactive reserve status will be excluded from the recall. Those recalled to service will get five months' notice.

The Marines currently have about 59,000 men and women serving in what's officially known as the individual ready reserve, former active-duty service members who still have time to serve on their mandatory eight-year commitment. Marine officials said they don't expect to activate more than 2,500.

The move follows similar call-ups by the Army, which has recalled about 5,100 former soldiers back to service since the Sept. 11, 2001, terrorist attacks. Most of those have been activated since 2004, and 2,100 remain on active duty, according to Army officials.