The Pentagon said on Thursday that National Guard and Reserve troops ordered to active duty since the Sept. 11, 2001, attacks will be offered medical coverage for up to eight years after resuming civilian life.

The move follows criticism by advocates for Guard and Reserve members that the Pentagon has relied heavily on these part-time troops to wage wars in Iraq and Afghanistan but has given them inferior benefits compared to regular active-duty personnel.

The Pentagon said the 400,000 part-time troops ordered to active-duty since the 2001 attacks may be eligible for the new benefits offered under the Pentagon’s Tricare health plan starting next month.

It said the program was expected to cost $70 million in fiscal 2005 and $394 million in fiscal 2006.

The large majority of Guard and Reserve members have medical coverage from civilian employers, but William Winkenwerder, assistant defense secretary for health affairs, said he expected at least tens of thousands to sign up.

The Pentagon has provided Guard and Reserve members and their families full medical benefits under the Tricare system while they were on active duty, but they could keep the health coverage for only six months after resuming civilian life.

The new plan would allow them to keep coverage for at least a year and up to eight years based on how long they served on active duty and how long they committed to remaining in the Guard or Reserve. To remain eligible, a person cannot leave the Guard or Reserve, said Thomas Hall, assistant defense secretary for reserve affairs.