After restrictions on women in combat are lifted in January, military officials estimate it will take up to two years before women actually will be "recruited, accessed, trained, tested and assigned" to some of the roughly 245,000 jobs now legally closed to them, according to a new Government Accountability Office report.

The GAO said the Pentagon should develop long-term plans to oversee the integration of women in combat after the official policy change in 2016.

The GAO study of the Defense Department's plans for opening all combat jobs to women comes as the deadline looms for the military's top brass to decide whether to eliminate all gender restrictions or offer a good reason not to do that by requesting a formal waiver to the forcewide policy.

Defense Secretary Ash Carter will have to approve any exemptions.

DoD's Office of Personnel and Readiness has kept a close watch on the service-specific efforts to study the issue and prepare for the official change to military policy. But top Pentagon civilian leaders have no plans for monitoring the services' followup implementation during the next several years, according to the GAO.

"Without ongoing monitoring of the services' and [Special Operations Command's] implementation progress in integrating previously closed positions and occupations, it will be difficult for DoD to have visibility over the extent to which the services and SOCOM are overcoming potential obstacles to integration," the report stated.

In addition, a lack of monitoring will leave DoD without enough information to give to Congress about progress on the issue, the GAO said.

In response to the report, the Pentagon agreed with the GAO's recommendation that top officials should keep a close eye on the changes after 2016.

"We recognize the importance of monitoring the long-term implementation progress of expanding combat service opportunities for women," Juliet Beyler wrote in a July 10 letter to the GAO.

Timelines for the initial implementation process will vary by service and military occupation, "but typically may require less than half a year to almost two years to complete the training part of the implementation process," Pentagon officials told the GAO.

It's been more than two years since then-Defense Secretary Leon Panetta set in motion plans to change the longstanding rule that technically excludes women from serving in combat roles — more than 300,000 jobs in all, many of them in Army and Marine Corps infantry and armor units.

Since then, the services have opened up more than 90,000 jobs to women. But the Army and Marine Corps have made no decisions about infantry and armor jobs, which may be the most controversial.

Both services are studying five key areas of concern: unit cohesion; women's health; equipment and gear; modifications to military facilities that may be required; and the level of interest among women in actually serving in combat jobs, known as propensity.

Most of the studies are ongoing, so it's too early to determine how the services will interpret or implement the findings, the GAO said.

Many troops say the combat exclusion rule that restricted women from jobs with combat units at the battalion level and below, last revised in 1994, did not reflect the ground-level risks faced by all troops in Iraq and Afghanistan regardless of their designation as a "combat" unit. About 300,000 women served in the two wars and more than 150 were killed.

Women are underrepresented in the flag and general officer ranks, and many female soldiers and Marines say the combat exclusion rule has harmed career prospects for women because most senior leaders in those services emerge from combat arms career fields.

Critics of the transition fear that introducing women into tightly-knit combat units, especially the special operations teams that run in small formations, will erode unit performance through a toxic mix of traditional chivalry, gender bias and sexual tension.