U.S. Secretary of State Rex Tillerson and South Korean Foreign Minister Yun Byung-se agreed to “further strengthen” the U.S. – South Korea alliance to respond to the North Korean nuclear issue, South Korea’s Ministry of Foreign Affairs (MOFA) announced on Tuesday.

Tillerson and Yun spoke over the telephone for the first time since Tillerson’s appointment at 0750 KST (1050 GMT) on Tuesday, sharing views on North Korean issues, including its nuclear program and ways to bolster the alliance, MOFA said.