Sens. Susan Collins and Joseph Lieberman have threatened to use subpoena power to force the Pentagon to live up to its promise to release the data used to support its base closing recommendations.

Unless the data are released promptly, they wrote in a letter to Defense Secretary Donald Rumsfeld on May 27, the Committee on Homeland Security and Governmental Affairs will investigate the Defense Department’s “decision-making process underlying its recommendations for potential improprieties.”

“As part of that investigation, the committee will issue a subpoena to the [Defense] Department to compel production of the information required by the Defense Base Closure and Realignment Act,” the senators wrote.

Collins, R-Maine, is chairwoman of the committee, and Lieberman, D-Conn., is the ranking Democrat.

The Pentagon has been under fire for missing its May 23 deadline to release the data. Officials promised Friday to release much of the data by this afternoon to congressional staffers who have security clearances.

The Defense Department has blamed the delay on security checks needed because some of the information is classified.

Only a complete release of data including e-mails, memoranda, spreadsheets, analyses, raw data, handwritten notes and telephone logs is acceptable, Collins and Lieberman wrote.

Connecticut was the hardest hit by the recommendations, with four facilities making the list, including the U.S. Naval Submarine Base in Groton. The state would lose about 8,600 jobs – nearly 30 percent of the net national job losses.

In Maine, nearly 8,000 jobs would be eliminated by closing the Portsmouth Naval Shipyard on the New Hampshire border and a Defense Finance and Accounting Service center in northern Maine, as well as stripping aircraft and half of the military personnel from Brunswick Naval Air Station.

The Pentagon’s announcement that it would provide the data by today came the same day Anthony Principi, chairman of the independent base closing commission, said the panel can’t do its job unless the material is released promptly.

“We cannot make informed decisions without the data, and that’s critical to our work,” he said Friday after meeting with officials from Maine and New Hampshire.