South Korea indirectly expressed regret over a senior North Korean official's derisive remarks about Seoul's efforts to help restart denuclearization talks between the North and the U.S.

Unification Ministry spokesperson Lee Sang-min said on Monday the two Koreas will have to respect each other and refrain from offensive language for the development of inter-Korean ties and the establishment of lasting peace on the Korean Peninsula.

The remarks come after North Korea's former nuclear envoy Kim Kye-gwan urged Seoul in a statement last Saturday to act "prudently" regarding the denuclearization talks, noting that Seoul is not part of them.

Kim said Seoul seems to still have lingering hope for "playing the role of mediator" between Washington and Pyongyang.

The former North Korean envoy added it is "presumptuous" for South Korea to meddle in the personal relationship between the leaders of the U.S. and North Korea. 

The statement comes after National Security Adviser Chung Eui-yong announced last Friday that Seoul conveyed a birthday message from U.S. President Donald Trump to North Korean leader Kim Jong-un.