The top nuclear envoys of South Korea, the United States and Japan held a conference call on Monday to discuss North Korea's plan to launch its first military spy satellite.

According to Seoul's foreign ministry, the country's chief nuclear envoy, Kim Gunn, and his U.S. and Japanese counterparts Sung Kim and Takehiro Funakoshi strongly urged the North to refrain from illegal launches that threaten regional peace.

The top envoys stressed that any launch using ballistic missile technology is an illicit contravention of multiple UN Security Council resolutions that cannot be justified in any way.

The trio agreed to closely cooperate to ensure that the launch by North Korea will be met with a stern, unified international response.

The talks came after Pyongyang on Monday notified Japan of a plan to launch a satellite between May 31 and June 11.