WASHINGTON (Yonhap News) ― North Korean leader Kim Jong-un is believed to have more than $1 billion in overseas secret bank accounts, according to a news report that cited an intelligence official.

The Washington Times quoted the unnamed official as saying there are reports that Kim and his family maintain at least $1 billion in slush funds in Switzerland, Austria and Luxembourg.

The U.S. is trying to ratchet up financial pressure on Pyongyang to curb its nuclear and missile programs.

The U.N. Security Council imposed new sanctions on the communist regime after its Feb. 12 nuclear test.

The official argues an effective way to squeeze Pyongyang financially would be pressing it to repay its debts.

“In order to cut off North Korea’s funds for developing weapons of mass destruction, we should trace and block the Kim family’s overseas secret funds in addition to calling for creditor companies to call on North Korea to repay its debts,” the official said.

Estimates put the amount of foreign debt owed by North Korea at $14 billion from some 30 countries.

North Korea owes Japan $400 million, Sweden $330 million, Iran $300 million, Germany $300 million, Thailand $260 million, Switzerland $100 million and Iraq $50 million, a Treasury official told the Washington Times. All of the nations are demanding repayment, but China and Russia are still lukewarm on the international debt repayment efforts.

China, a key North Korean patron, is owed $6.98 billion by Pyongyang and Russia is owed $1.1 billion, mainly from transfers of military assets and other assistance, the newspaper said.

“Treasury has been using tools at its disposal to increase financial pressure on the North Korean regime by targeting individuals and entities responsible for facilitating payments connected to North Korea’s nuclear and ballistic missile program, as well as financial institutions such as the Foreign Trade Bank, which has served as a key node for the regime’s foreign exchange,” the Treasury official was quoted as saying.