The financial noose is tightening around North Korea as international banks sever ties with the nation — a move championed by the United States, a top Treasury Department official says.

The United States has accused Pyongyang of spreading weapons and missile technology to other countries, counterfeiting U.S. currency and trafficking drugs. It wants to see the reclusive, communist-led regime financially incapacitated.

"There is sort of a voluntary coalition of financial institutions saying that they don't want to handle this business anymore and that is causing financial isolation for the government of North Korea," Stuart Levey, the Treasury Department's undersecretary for terrorism and financial intelligence, said in an interview Monday with The Associated Press.

"They don't want to be the banker for someone who's engaged in crime, as the North Korean government is," he said.

CountryWatch: North Korea

Banks in Singapore, Vietnam, China, Hong Kong and Mongolia are opting not to do business with North Korea, Levey said.

"Is there a complete cutoff, so that they can't get banking anywhere? No, that's not the case, but they're having a very difficult time finding banking services," he said. "You're seeing a near complete isolation."

Ignoring warnings from the United States and other countries, North Korea test-fired seven missiles last month, raising tensions in the region.

The United States is considering tightening economic sanctions against North Korea, although Levey avoided specifics.

Last year, the Treasury department took action against a bank, Banco Delta Asia SARL, in Macau, a special administrative district of China, for what it said were lax money-laundering controls, alleging the bank helped North Korea distribute counterfeit currency and engage in other illicit activities. The department also has moved against other companies, claiming they were helping North Korea spread weapons of mass destruction.

Because of the financial clampdown, North Korea has refused to resume six-nation talks meant to persuade it to abandon its nuclear weapons program.

Some analysts worry that the financial restrictions are only deepening the North's isolation. This, they argue, has allowed North Korea to push ahead with its weapons programs. North Korea accused the United States of tracing North Korean accounts in banks in at least 10 countries and called this "a gangster-like act."

In other matters, Levey called Iran a "central banker of terror" that provides millions of dollars a year to bankroll terrorist acts carried out by the militant group Hezbollah.

"Iran is like the elephant in the room, if you will. ... They are the central banker of terror. It is a country that has terrorism as a line item in its budget," he said.

Levey's comments came as the United States repeated its resolve to pursue U.N. sanctions against Iran unless the country stops enriching uranium, a key step in making nuclear weapons.

Tehran faces a Thursday deadline imposed by the U.N Security Council to halt its uranium-enrichment program or face political and economic sanctions. Levey didn't talk about what form those sanctions could take.

Levey said the United States is working not only to halt Iran's nuclear ambitions but to clamp down on its funding of Hezbollah and its role in the recent bloodshed in Lebanon.

He estimated that Iran was providing Hezbollah hundreds of millions of dollars a year in financial support, in addition to military equipment. Levey said money flowing from Iran also helps finance other terrorist groups, including Hamas and the Palestinian Islamic Jihad.

In other matters, Levey said although terrorists and other criminals are always looking for new ways to move money, "the banking system still is the most efficient way and the preferred way."

He also defended the usefulness of a once-secret program that gives the U.S. government access to a massive international data base of financial information to catch suspected terrorists. The existence of the program, which started shortly after the 2001 terror attacks in the United States, was made public by news organizations in June.

The department intends to keep the tracking program, Levey said. It will take time to assess whether disclosure of the program has led terrorist financiers to change their behavior, he added.

"We have got an adversary out there that we are trying to do everything to stop. They may be evil, but they are very smart," Levey said.

The threat to the United States is real, he said. "This is not some made-for-TV movie."