The five permanent members of the United Nations Security Council said in a joint statement that North Korea and Iran are hindering international efforts to stem the proliferation of nuclear weapons.

Representatives from the United States, China, the United Kingdom, France and Russia released the statement after a preparatory meeting in Geneva, Switzerland ahead of the review of the non-proliferation treaty that will take place in 2015.

The five nations said North Korea’s February nuclear test and Iran’s campaigns to obtain nuclear capabilities were a serious challenge against non-proliferation efforts and re-expressed their concerns.

The statement said an effective safety system from the International Atomic Energy Agency was needed to stop the proliferation of nuclear arms and added they would seek ways to resolve the nuclear issues in North Korea and Iran through peaceful and diplomatic measures.