WASHINGTON - White House Counsel Gregory Craig, who has played a central role in the Obama administration's rocky efforts to close the U.S. military prison at Guantanamo Bay, said on Friday he was resigning.

Craig's departure marks the highest-profile White House resignation since President Barack Obama took office in January and followed reports of dissatisfaction within the administration over his management of Guantanamo policy.

Obama's promise to shut the internationally condemned detention center in Cuba by January 22 has run into serious obstacles, making it unlikely the foreign terrorism suspects detained there can be transferred to meet the deadline.

Neither Craig nor the White House gave any immediate reason for his resignation as Obama's top lawyer, except to say he was returning to private practice.

Craig will be replaced by Bob Bauer, a Democratic lawyer who has worked for Obama for years, the White House said.

Greg Craig is a close friend and trusted advisor who tackled many tough challenges as White House Counsel, Obama said in a statement released while visiting Tokyo at the start of an Asian tour.

Because of Greg's leadership, we have confirmed the first Latina justice on the Supreme Court, set the toughest ethics standards for any administration in history, and ensured that we are keeping the nation secure in a manner that is consistent with our laws and our values, Obama said.

Craig was initially assigned to the search that produced the successful Supreme Court nomination of Justice Sonia Sotomayor before the task was turned over to other administration officials.

He also played a leading role in revising Bush-era policies for interrogation of terrorism suspects that had drawn heavy international criticism.

It has been an honor to work for you, Craig said in his resignation letter to Obama. We have helped develop a legal framework that will deal with threats to our national security in a way as to protect our nation from harm while remaining true to our most fundamental values.

Craig said his resignation would be effective on January 3.

The announcement came on the same day the administration said an alleged mastermind of the September 11, 2001 attacks, Khalid Sheikh Mohammed, and four others would be sent from Guantanamo for prosecution in a criminal court in New York.

(Reporting by Matt Spetalnick, editing by Vicki Allen)