six-year struggle to uncover Osama bin Laden's financial network failed because American officials did not skillfully use the legal tools they had, did not realize they needed stronger weapons, and faced resistance at home and abroad, officials involved in the effort say.

Federal officials say they have not persuaded foreign banks to open their books to investigators and that in this country, a law that would have allowed the United States to penalize foreign banks that did not cooperate was blocked last year by a single United States senator.

Current laws and regulations give the government less authority to seize the assets of terrorists than of drug cartels, one federal investigator said; it may seize only assets that are the direct proceeds of terrorist violence. For drug cartels or organized crime gangs, it can seize any assets used to support their activities.

Investigators also attribute their inability to pierce Mr. bin Laden's financial network to an ancient system of cash transfers based on trust, not detailed records, that they say has spread from countries like Pakistan into the United States.

Since last week's attacks, proposals to curb money laundering by terrorists have suddenly gained support among old opponents — including the Bush administration — after languishing for two years. The White House says it now wants an aggressive attack on money laundering, including stepped-up seizure of assets.

The bin Laden organization operates in 35 countries and needs to move money to its members, American intelligence officials say. Tracing the money could reveal not only terrorists' sources of support, but their intentions.

But present and former government officials say that since the mid- 1990's, they did not fully use the legal tools they had to wage this difficult fight. "We could have starved the organization if we put our minds to it," said Richard Palmer, who gained experience in money laundering as the Central Intelligence Agency's station chief in Moscow during the 1990's. "The government has had the ability to track these accounts for some time."

Congress is now reviving a proposal killed last year by Senator Phil Gramm, the Texas Republican who was then chairman of the Senate Banking Committee. The bill, introduced by the Clinton administration, would give the Treasury secretary broad power to bar foreign countries and banks from access to the American financial market unless they cooperated with money-laundering investigations. It was strongly opposed by the banking industry and Mr. Gramm.

"I was right then and I am right now" in opposing the bill, Mr. Gramm said yesterday. He called the bill "totalitarian" and added, "The way to deal with terrorists is to hunt them down and kill them."

But the bill is gathering support from both parties. "I would be amazed if there is not a sea change," said Senator John Kerry, the Massachusetts Democrat, who is sponsoring the bill with Senator Charles E. Grassley, Republican of Iowa. He said the opposition was based on "ridiculously phony" arguments.

Even after the attacks last week, the banking industry continues to doubt the need for new rules to combat money laundering, a lobbyist said.

Most experts say the funds used to finance the attacks here probably came into this country in small amounts either through wire transfers or through the use of brokers that belong to a paperless underground banking system.

That system of brokers is often referred to by its Hindi name, "hawala," meaning "in trust." It enables individuals to transfer sizable sums of cash from their country to recipients in another country without the funds ever crossing borders. The system, which has spread to the United States, is particularly popular in countries like Pakistan and India where people want to avoid paying taxes or bribes to officials when transferring money across borders, experts said.

"Somebody will come into the office of a hawala broker in Pakistan and say, `I want $100,000 to get to somebody in Vero Beach who is going to come in and identify themselves as Cupid,' " said Jonathan M. Winer, who led the State Department's international law enforcement efforts from 1994 to 1999 and now practices law in Washington.

The Pakistani broker, Mr. Winer explained, will contact a counterpart in the United States, often using the Internet, then mail him a chit or agree on a code word to complete the transaction.

Mr. Winer said such brokers might have been used to transfer sizable sums of money destined for terrorists in this country because carrying large amounts of cash posed too many risks.

"The two brokers have absolute trust in each other," said Rowan Bosworth-Davies, an expert on money laundering at the Control Risks Group. "They often come from the same clan and that is why nothing is written down or records kept."

Congress passed a law in 1993 requiring check-cashing businesses and informal financial enterprises like hawalas to register with the government and report transactions over $3,000. But the Clinton administration did not publish all the regulations until 1999. The Bush administration ordered a further delay until June 30, 2002. Jimmy Gurule, the Treasury under secretary for enforcement, said yesterday that the administration, in light of last week's attack, might move up the date.

The effort to track the bin Laden group's money began in earnest when President Bill Clinton signed a classified presidential order on Oct. 21, 1995. The secret order, Presidential Decision Directive 42, ordered the Departments of Justice, State and Treasury, the National Security Council, the C.I.A. and other intelligence agencies to increase and integrate their efforts against international money laundering by terrorists and criminals.

The government agencies joined together to try to penetrate the bin Laden network of businesses, charities, banks and front companies. They failed.

The ball was handed to people who were generally incompetent to handle the intricate task, said one Clinton administration official directly involved in the effort to drain or divert the money flowing in and out of the bin Laden organization.

The government agencies given the job suffered from "a lack of institutional knowledge, a lack of expertise," said William Wechsler, a National Security Council staff member under Mr. Clinton. "We could have been doing much more earlier. It didn't happen."

Then attackers blew up two American embassies in Africa in August 1998. Richard A. Clarke, the government's counterterrorism coordinator, set up a new government team. He ordered it to find out how much money the bin Laden organization had, where it came from, how it moved around the world — and to stop it.

"We had only marginal successes," said Mr. Wechsler, who led the new team in 1998 and 1999. The United Arab Emirates imposed money laundering laws and China banned flights by the Afghan state airline, Ariana, at the United States' urging, officials said.

The lack of great success was "mostly due to the limited assistance we received from key countries abroad," Mr. Wechsler said. He blamed "their lack of political will or weaknesses in their laws which fail to effectively regulate their financial institutions and charities."

Until last week's attacks, the Bush administration was not much more enthusiastic about new money laundering laws than Mr. Gramm. Led by its chief economic adviser, Lawrence B. Lindsey, the administration did not want to pressure international banks in the United States and elsewhere to open their books.

Now the White House is setting up a new agency, called the Foreign Terrorist Asset Tracking Center, run by the Treasury Department with help from law enforcement and intelligence services, to try anew to track bin Laden's finances.

The financial architecture of the bin Laden organization has not changed radically since he set up operations near the Khyber Pass in the mid-1980's and worked side by side with the C.I.A. to support the rebels fighting Soviet forces in Afghanistan, United States officials said.

"The money movement and fund- raising system is the same," Mr. Wechsler said.