The International Committee of the Red Cross made the announcement on Friday after a meeting with top US officials.
But ICRC President Jakob Kellenberger said he had yet to see "concrete results" on other concerns he expressed about the status of the roughly 660 non-US citizens imprisoned at the Cuba base.
Kellenberger also said the United States had not yet told the ICRC when it would get access to former Iraqi President Saddam Hussein.
The United States announced on 9 January it had formally designated him an enemy prisoner of war, entitling him to a visit by the ICRC.
'Legal black hole'
Kellenberger met on Friday with Deputy Defense Secretary Paul Wolfowitz after meeting on Thursday with Secretary of State Colin Powell and National Security Adviser Condoleeza Rice.
The United States two years ago began holding foreign nationals caught in what President George Bush calls the global war on terrorism at a specially built detention facility at the Guantanamo base. Most were captured in Afghanistan.
"If they are not considered prisoners of war... then they have to be charged with a crime and given access to an attorney and to some kind of tribunal before which they can adjudicate their status. And that is, of course, not happening"
International organisations including the ICRC have accused the United States of condemning the prisoners to a "legal black hole".
Kellenberger visited Washington in May, demanding prisoners be allowed due process of the law and seeking changes at the Guantanamo camp.
He said these concerns had not been adequately addressed, expressing disappointment that two years after the first prisoners arrived, they still face indefinite detention beyond the reach of the law.
Using a secretive review process, the United States has released 84 Guantanamo prisoners and sent four others to Saudi Arabia for continued detention.
"Mr Wolfowitz has told me that they will accelerate the review process of the people in Guantanamo. And this accelerated review process, it would be my hope, could then lead also to a speeding up of the releases," Kellenberger said.
The ICRC chief said Wolfowitz, Powell and Rice "seemed sincerely receptive to our concerns and challenges".
"But they did not give detailed answers to these requests," Kellenberger said. "I hope now that our dialogue will lead to concrete results."
The ICRC chief pressed for access to the unknown number of "terrorism" suspects seized by the United States and held at undisclosed locations, expressing concern for their fate.
Donald Rumsfeld has labeled the
Guantanamo inmates 'terrorists'
The Pentagon offered no details about the meeting. The Defense Department is in the final stages of planning for trials by special military tribunals of some of the detainees.
Critics have accused the United States of violating the Geneva Conventions, noting the decision to deny detainees prisoner-of-war status entitling them to numerous legal rights in favour of the designation "unlawful combatants".
"If they are not considered prisoners of war, as apparently they are not in this case by the US, then they have to be charged with a crime and given access to an attorney and to some kind of tribunal before which they can adjudicate their status. And that is, of course, not happening," Amnesty International USA Executive Director William Schulz said.
And Human Rights Watch said the world still does not know who the detainees are, what they are accused of doing, or when they might be charged or released.