Officials from 70 countries around the world held an anti-WMD proliferation conference in Washington on Wednesday and agreed to work closely together to ensure that no weapons of mass destruction technology is transferred to North Korea, a diplomatic source said.

North Korea was a key topic for the Mid-level Political Meeting of the U.S.-led Proliferation Security Initiative (PSI), an international coalition aimed at stopping the spread of WMDs, related material and technology, as it came just weeks after Pyongyang's fourth nuclear test.

Mindful of the nuclear test, participants agreed to step up joint efforts to prevent the transfer of WMD technology to the communist nation, the source told Yonhap News Agency, speaking on customary condition of anonymity.

U.S. Assistant Secretary of State for International Security and Nonproliferation Thomas Countryman hosted Wednesday's conference designed to set a course for the future by building on the results achieved at the 2013 High-Level Political Meeting that was held in Warsaw, Poland, to mark the 10th anniversary of the initiative.

The PSI was launched in 2003 under the George W. Bush administration and a total of 105 countries around the world have since endorsed the initiative that calls mainly for maritime interdiction of suspected shipments. North Korea is among the major targets of the initiative.

Pyongyang has strongly protested against the drive, saying it amounts to a naval blockade.

Leading the PSI are 21 countries in the Operational Experts Group (OEG), and South Korea is one of them. (Yonhap)