In a series of diplomatic cables spanning several years, published by the WikiLeaks whistleblowing website on Sunday, the state department details how such groups continue to seek financing in Saudi Arabia, often posing as pilgrims visiting the Muslim holy sites.
"Saudi Arabia remains a critical financial support base for al-Qaeda, the Taliban, LeT, and other terrorist groups, including Hamas, which probably raise millions of dollars annually from Saudi sources, often during Hajj and Ramadan," Hillary Clinton, the US secretary of state, said in one cable sent in December 2009.
"In contrast to its increasingly aggressive efforts to disrupt al-Qaeda's access to funding from Saudi sources, Riyadh has taken only limited action to disrupt fundraising for the UN 1267-listed Taliban and LeT-groups that are also aligned with al-Qaeda and focused on undermining stability in Afghanistan and Pakistan."
The memo credited the Saudis with "significant progress" under US pressure to deal with the issue, especially disrupting Al-Qaeda's finance channels.
However, it said that "Riyadh has taken only limited action" to interrupt the flow of money to Taliban and LeT-associated groups which have launched attacks in Afghanistan, Pakistan and India.
In July 2009, Richard Holbrooke, the US special representative to Afghanistan and Pakistan, said that the Taliban get more of its funding from wealthy Gulf donors than from the drug trade for which Afghanistan has long been famous.
According to the cable, the annual hajj pilgrimage posed a particular problem for Saudi authorities attempting to stop the flow of money to armed groups.
"Hajj was still a big problem for the Saudis, since they could not refuse to let pilgrims enter the country. Some of the non-Saudi terrorism detainees in Saudi Arabia had entered as pilgrims," it said.
A cable sent in August 2009 detailed how Pakistan's Jamaat-ud-Dawah, which the US accuses of being a front for Lashkar-e-Taiba, raised funds through "private donations, non-governmental organisations (NGOs), madrassas, and businesses spread throughout South Asia, the Middle East, and Europe".
"Some of JUD's budget, using funds raised both from witting donors and by fraud, is dedicated to social services or humanitarian relief projects, while some is used to finance LT operations," it said.
The cable said that Lashkar-e-Taiba officials were operating front companies in Saudi Arabia to move funds that could be used to carry out attacks.
US officials have also complained of direct donations by wealthy individuals and a reluctance by governments to monitor charities.
Informal money transfer networks called hawala, or worker remittances compound the problem.
Kuwait, another key US ally in the region, comes in for criticism in the memo sent by Clinton in 2009 for being the sole nation in the six-member Gulf Co-Operation Council (GCC) that does not have a specific law criminalising the financing of "terrorist" groups.
"The GOK [government of Kuwait] at times has obstructed or been slow to enforce UN-mandated asset freezes of Kuwait-based entities," it said.
Qatar, which hosts a large US military base is also singled out its "largely passive approach" to co-operating with Washington on tackling the financing of armed groups.
"Al-Qaeda, the Taliban, UN-1267 listed LeT, and other terrorist groups exploit Qatar as a fundraising locale," the state department memo said.
"Although Qatar's security services have the capability to deal with direct threats and occasionally have put that capability to use, they have been hesitant to act against known terrorists out of concern for appearing to be aligned with the US and provoking reprisals."
United Arab Emirate-based donors were identified as having "provided financial support to a variety of terrorist groups".
"The point can be emphasised that the UAE's role as a growing global financial centre, coupled with weak regulatory oversight, makes it vulnerable to abuse by terrorist financiers and facilitation networks," the state department cable said.
In another cable from December 2009, Howard Mendelsohn, the US treasury department acting assistant secretary of the office of intelligence and analysis, stated his belief that the "Taliban and Haqqani Network [a Pakistan-based group fighting Nato forces in Afghanistan are believed to earn money from UAE-based business interests".
"Treasury analysts provided information on ... two senior Taliban officials who have made multiple fundraising visits to the UAE, according to U.S. intelligence," the cable said.
"The UAE security services were not familiar with either individual and asked for additional identifying information."