Financial institutions around the world should choose between doing business with North Korea and being denied access to the U.S. financial system or severing dealings with the communist nation, the chairman of the U.S. House Foreign Affairs Committee said.

Rep. Ed Royce (R-CA) made the remark at the end of his two-day visit to Seoul, referring to the U.S. blacklisting last week of the North as a "primary money laundering concern" in a move designed to cut off Pyongyang from the international banking system, according to his office.

The designation "impacts all financial institutions, anywhere, who now have a choice to make between doing business with North Korea and being cut off from financial transactions with the United States and the international financial system," Royce said.

The designation came as part of the North Korea Sanctions and Policy Enhancement Act pushed forward in February to punish Pyongyang for conducting its fourth nuclear test in January and a long-range rocket launch the following month in violation of U.N. resolutions.

Royce is a key author of the legislation.

"Given the threat posed by North Korea, now is the time to make it really difficult for Kim Jong-un to pay his generals, make it difficult to keep the production lines open for missiles, and make it difficult for him to acquire parts on the black market ... and we must move in unison to take decisive action," Royce said.

Royce's visit to Seoul included meetings with South Korean Defense Minister Han Min-koo, National Security Advisor Kim Kwan-jin and Vice Foreign Minister Lim Sung-nam, as well as U.S. Forces Korea Commander Vincent Brooks and U.S. Ambassador Mark Lippert.

"I've never seen the [U.S.-South Korea] relationship as strong as it is today, and I think it's going to get stronger ... Republicans and Democrats in Congress are very committed to the alliance," Royce said, according to his office. (Yonhap)