Lawyers for the 9/11 plot suspects on Thursday sought to delay until this summer filing memos on why the terror tribunal should not go forward as a capital case.

If a senior Pentagon official agrees, the soonest the alleged mastermind Khalid Sheik Mohammed and his accused four co-conspirators would get initial appearances at Guantánamo’s Camp Justice would be around the next Sept. 11 anniversary.

At issue is an ethical dispute over how the Guantánamo prison commander is reviewing confidential communications between Pentagon lawyers and their captive clients. Defense lawyers stopped sending so-called privileged mail to their clients late last year after the Chief Defense Counsel, Marine Col. Jeffrey Colwell, declared the policy of reviewing mail unethical.

Colwell said Thursday that all five 9/11 defense teams were seeking the delay because the controversial camp mail policy “complicated the attorneys’ ability to prepare.”

Prosecutors are now working with the camps commander, Rear Adm. David B. Woods, to devise a new mail system that’s blessed by the chief war court judge. No solution is expected before April.

The attorney for Ramzi bin al Shibh, a Yemeni accused of orchestrating part of the mass murder from Hamburg, Germany, asked for a delay until August. Another lawyer asked for a four-month delay on behalf of Mustafa al Hawsawi, who is accused of helping to move some of the money that financed the Sept. 11 hijackers’ travels.

A Pentagon spokesman, David Oten, said the request for an extension was under consideration.

The Obama administration cleared the way for a 9/11 tribunal in April. Prosecutors swore out death-penalty charges May 31.

Since then, the Pentagon has been assembling defense teams. .

The teams are supposed to write a senior Pentagon official overseeing the war court, retired Vice Adm. Bruce MacDonald, by Monday on why the case shouldn’t go forward.

A Navy war-crimes prosecutor defended the new mail policy at a hearing last month by disclosing that a copy of al Qaida’s now defunct Inspire magazine had reached the detention center. Prison-camp commanders won’t discuss when or how the alleged security breach happened in the Pentagon’s showcase prison, which has a staff of 1,875 U.S. forces and civilians and 171 detainees.