NEW YORK (Reuters) - Foreign ministers for the United States, Japan and South Korea met in New York on Sunday, ahead of U.N. meetings, to discuss stepped-up measures against North Korea and expand collaboration with one another after Pyongyang’s fifth and largest nuclear test.

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The Sept. 9 blast was in defiance of U.N. sanctions that were tightened in March.

The meeting between U.S. Secretary of State John Kerry, Japanese Foreign Minister Fumio Kishida and their South Korean counterpart, Yun Byung-se, was the first since the latest nuclear test. It will be one of the main issues discussed by world leaders at the United Nations General Assembly this week.

In a joint statement, the ministers said North North’s disregard for multiple U.N. resolutions prohibiting its missile and nuclear programs called for even stronger international pressure.

North Korea has been testing nuclear weapons and ballistic missiles at an unprecedented rate this year under leader Kim Jong Un.

“They discussed the important work currently taking place in the Security Council to further sanction North Korea and considered other possible measures of their own, in particular ways to further restrict revenue sources for the DPRK’s missile and nuclear programs, including through illicit activities,” the ministers’ statement said.

“They reaffirmed that they remain open to credible and authentic talks aimed at full and verifiable denuclearization of the DPRK,” the statement said, referring to the country’s formal name, the Democratic People’s Republic of Korea.

The United States has said it is willing to negotiate with the North if the country commits to denuclearization, which Pyongyang has refused to do.

Washington has pressed Beijing, which is Pyongyang’s most important diplomatic backer and trading partner, to do more to rein in North Korea.

China has expressed anger with North Korea for its largest nuclear test to date, but has not said directly whether it will support tougher sanctions. It has said it believes sanctions are not the ultimate answer and called for a return to talks.