Washington (CNN) -- Secretary of Defense Robert Gates said Thursday that congressional opposition makes the likelihood of closing the detention center at Guantanamo Bay, Cuba, "very, very low."

Gates' remarks at a hearing of the Senate Armed Services Committee was one of the clearest signs yet of the dim prospects for carrying out one of President Barack Obama's earliest executive orders: to shutter the facility where the U.S. military has detained suspected terrorists since 2002.

"I think we are in the position, frankly, the prospects for closing Guantanamo, the best I can tell, are very, very low given very broad opposition to doing that here in the Congress," Robert Gates told the Senate Armed Services Committee.

Asked what the United States would do about holding so-called high-value targets, which presumably would include Osama bin Laden and other al Qaeda leaders, Gates responded, "I think the honest answer to that is, we don't know.

"If we capture them outside the area where we are at war and are not covered by the existing war authorizations, one possibility is for a person to be in the custody of their home government," Gates said. "Another possibility is that we bring them to the United States.

Retired Navy Cmdr. Kirk Lippold, Senior Fellow for Military Families United, said in a statement that the admission shows the administration "is finally realizing that Guantanamo Bay remains the only facility suitable for detaining top al-Qaeda operatives and other terrorists."

"It is essential to keep GITMO open as a state of the art intelligence collection facility and terrorist detention center,"

said Lippold, who was commander of the USS Cole, the Navy destroyer attacked by a suicide bomber, killing 17 and wouding 37, in October 2000. "The nation's security is not something that should be subject to guesswork. A plan must be put into place for terrorists who are captured and that plan must start at Guantanamo Bay."

On January 22, 2009, two days after his inauguration, Obama issued an executive order requiring that the Guantanamo Bay detention facility be closed within a year, seemingly fulfilling an oft-made promise during his campaign. But controversy over whether to try the suspected terrorists imprisoned there in federal court or in military commissions brought the issue to a legal and political stalemate.

In an interview on CNN's "State of the Union" in December 2010, then-press secretary Robert Gibbs encapsulated the problem from the administration's perspective: "Well, obviously, there are prohibitions, legislatively, on the transfer of some of the prisoners. Some would be tried in federal courts, as we've seen done in the past. Some would be tried in military commissions, likely spending the rest of their lives in a maximum security prison that nobody, including terrorists, have ever escaped from. And some, regrettably, will have to be indefinitely detained."

CNN's Gabriella Schwarz contributed to this report.