"There is a great deal of frustration among members of the commission," the panel's spokesman, Al Felzenberg, told United Press International Sunday.
The use of a subpoena would mark a breakdown in relations with a White House that initially opposed the establishment of the commission, but says it has been cooperating. Felzenberg said it would be a last resort.
"We hope we don't have to use (our subpoena power), but at the same time, we must have the documents we need to do our work," he said. "We're not going to go on (negotiating) like this indefinitely."
White House spokesman Brian Besanceney told UPI Sunday that the administration was co-operating in an "unprecedented" manner with the inquiry. "We have turned over more than two million pages of documents," he said.
Negotiations over access to highly classified national security documents -- including the so-called presidential daily briefings that summarize the most important threats to the nation -- have been continuing for several months.
Over the summer, there were reports that a PDB in August 2001 had warned of an al-Qaida plot to hijack U.S. airliners. The Islamic terror network is thought to have carried out the Sept. 11 attacks, in which four hijacked airliners were used as missiles to kill more than 3,000 people.
Felzenberg would not give a deadline for the subpoena, but said the commission did not want "to go in to the Thanksgiving and Christmas holidays still negotiating."
Some senior intelligence figures have been skeptical that the commission will ever get to see the PDBs -- which are generally considered the country's most sensitive national security documents.
"If they're trying to subpoena the president's daily brief on intelligence," Sen. John D. Rockefeller, D-W.Va., told NBC's "Meet The Press" Sunday, "I would think that would be pretty hard to get."
An administration official, who spoke to UPI on condition of anonymity, echoed that sentiment. "There are documents we do not feel it is appropriate to make available," the official said. But he added that negotiations were continuing, "We're not at that point (of a subpoena) yet. We're still talking to the commission, trying to work out how we can accomplish our shared goal of letting them complete their work."
The subpoena threat -- first issued by the commission chairman, former GOP New Jersey Gov. Thomas H. Kean, to The New York Times -- is the first time the panel's leadership has publicly suggested they might have to fight the White House in court to get the documents they say they need.
But it is the latest shot across the bows of an administration that some commissioners have said is dragging its feet in an effort to run out the clock. The panel -- which is mandated to report by May 2004 -- is now more than half of the way through its time.
Senior Republicans, including Sen. John McCain, R-Ariz., have said that they will try to get the statutory deadline for the commission extended if more time is needed. But any extension raises the prospect of a highly sensitive report being published as the country enters an election campaign likely to be dominated by national security issues.
The political price tag for any non-cooperation by the administration is likely to be high in other ways, too.
Asked Sunday whether the White House was dragging its feet, Sen. Chuck Hagel, R-Neb., said, "I hope not.
"They have an opportunity to come forward with the requested documentation," he told NBC's "Meet The Press."
"It's definitely in their interest, certainly in the interest of this country. Americans and our allies across the world must have confidence in our leadership."
In a series of progress reports since June, the commission has repeatedly warned that its patience was running out.
Relatives of some of the victims of the Sept. 11 attacks have criticized the commission's public hearings for being too vague and too orientated toward future policy, rather than establishing what went wrong and why.
Sunday, commission officials suggested that this was in part a product of the slow pace at which they were getting access to the papers they need.
"We want to be able to hold more narrowly focused and deeper public hearings," said Felzenberg, "but to get to that point, we have to know that we have been through every relevant document."
Earlier this month, the panel decided to issue a subpoena to the Federal Aviation Administration after what the FAA said was a communications failure that resulted in it not handing over dozens of box loads of documents the commission said it needed.