"If I could somehow snap my fingers and cut off the funding from one country, it would be Saudi Arabia," Stuart Levey, the under secretary of the Treasury in charge of tracking terror financing, told ABC News.
Despite some efforts as a U.S. ally in the war on terror, Levey says Saudi Arabia has dropped the ball. Not one person identified by the United States and the United Nations as a terror financier has been prosecuted by the Saudis, Levey says.
"When the evidence is clear that these individuals have funded terrorist organizations, and knowingly done so, then that should be prosecuted and treated as real terrorism because it is," Levey says.
Among those on the donor list, according to U.S. officials, is Yasin al Qadi, a wealthy businessman named on both the U.S. and U.N. lists of al Qaeda financiers one month after the 9/11 attacks.
Al Qadi, who has repeatedly denied the allegations, remains free, still a prominent figure in Saudi Arabia.
Al Qadi's London-based attorney, Guy Martin of Carter-Ruck law firm, said the United States has never produced any evidence in support of the allegations against his client.
"He hasn't been tried, let alone convicted, anywhere in any jurisdiction in the world," said Martin. "While allegations have been made, there have been no formal criminal proceedings."
"This is a financial Guantanamo to my client who is the victim of a gross and on-going miscarriage of justice," said Martin. "This is a Kafka situation where people are put on this list with no due process."
While the Saudi embassy had no comment regarding Levey's specific allegations, a spokesman did note that after the Sept. 11 attacks, the country took prompt action and "required Saudi banks to identify and freeze all assets relating to terrorist suspects and entities per the list issued by the United States government." The statement went on to say that "Saudi banks have complied with the freeze requirements and have initiated investigations of transactions that suspects linked to Al Qaeda may have undertaken in the past."
U.S. officials say they are equally frustrated with what they call the empty promises of Pakistan to go after al Qaeda's sanctuaries in their country.
Pakistan says it is willing to take action if the U.S. provides details.
"If they had specific information, they should share it with us, and we would go after them," Pakistani Ambassador to the U.N. Munir Akram told ABC News.
When asked whether the U.S. can trust his country, Ambassador Akram said, "Well, if the U.S. doesnâ€™t trust Pakistan, how can Pakistan be an ally of the U.S.?"
A question echoed by many in the U.S.
With fresh funds and a safe haven, al Qaeda has been able to recruit and train a new class of terrorists as well as send out a stream of new propaganda tapes.
Just today, al Qaeda's leader Osama bin Laden was seen on a second video this week, introducing the video will of one of the 9/11 hijackers.
"And it remains for us to do our part," bin Laden said as he held up 9/11 hijacker Waleed al Shehri's life as an example. "So I tell every young man among the youth of Islam: it is your duty to join the caravan until the sufficiency is complete and the march to aid the High and Omnipotent continues."
U.S. officials fear there are more like al Shehri heeding bin Laden's call and coming now from Pakistan.
"The consequence is that there is in effect a sanctuary in the northwest part of Pakistan, just like the sanctuary that used to exist before we invaded Afghanistan," Richard Clarke, the former White House counterterrorism official and now ABC News consultant, said.
Rhonda Schwartz and Maddy Sauer contributed to this report.
This post has been updated.