While Iran and the West act out a diplomatic war of words, the U.S. is already fighting a bloodless war to keep Iran from obtaining nuclear weapons.

But the key players in this conflict aren't soldiers, it's the international financial system, as the new FOX News documentary "Iran: The Ticking Bomb" reports.

“The players are those financial institutions, banks, commercial companies. There are players who are playing on the Iranian part of the board,” a top Western intelligence official, who spoke on the condition of anonymity, tells FOX News. “There are players who are playing on the other side of the board.”

The U.S. Treasury is among the agencies pressuring banks worldwide to keep Iran from an influx of cash.

Click here to watch exclusive Web video from the documentary.

“They do need access to the international financial system in order to move money,” said Stuart Levey, the undersecretary for terrorism and financial intelligence at the U.S. Treasury. “And they're finding that, as the private sector is reacting to the kind of information that we've made available, they're finding it quite painful.”

Levey is applying new kinds of pressure on Iran's financial system, such as calling upon major foreign banks to explain how they might inadvertently be financing terror and Iran's nuclear program.

Two Iranian banks have been targeted: Bank Saderat for supporting terrorism and Bank Sepah for aiding in the proliferation of Iran’s nuclear and missile programs.

Click here to view a fax linking Bank Sepah to a Chinese firm (PDF).

Click here to see a fax from a Dubai firm requesting payment to Iran's largest bank (PDF).

But many Western banks may still be inadvertently caught up in Iran's financial web of front companies and secret transactions. That web is unraveled in the documentary.

"Iran: The Ticking Bomb," a FOX News documentary exploring Iran's support of global terrorism, its pursuit of nuclear weapons and its proxy war with the United States, airs at 9 p.m. on Sept. 29 on the FOX News Channel.