Top nuclear envoys of South Korea and the U.S. have held phone talks to discuss the latest missile launch by North Korea.

According to Seoul's foreign ministry, Noh Kyu-duk, special representative for Korean Peninsula peace and security affairs, spoke on the phone with his American counterpart Sung Kim on Sunday.

The talks came after the South Korean military said the North fired a ballistic missile from the Sunan area in Pyongyang toward the East Sea at 7:52 a.m. Sunday.

The top nuclear envoys reportedly shared their assessments of the North's move and expressed "deep concern and regret."

The ministry said the two sides also agreed that the allies will maintain a unified defense posture and continue diplomatic efforts to engage North Korea in dialogue.