A senior U.S. diplomat met with his counterparts in Seoul Thursday to discuss ways to condemn the Democratic People's Republic of Korea (DPRK) at the United Nations Security Council for the sinking of a South Korean warship.

U.S. assistant Secretary of State for East Asia and Pacific Affairs Kurt Campbell, who is on a two-day visit to Seoul, met with S. Korea's foreign minister Yu Myung-hwan and vice foreign minister Chun Yung-woo, separately, as Seoul steps up its diplomatic drive to convince the U.N. Security Council members to punish Pyongyang torpedoing the warship and taking 46 lives.

"We're determined to show that our alliance is very firmly together during an absolutely critical period," Campbell was quoted by Yonhap News Agency as telling Yu at the start of their meeting.

The two agreed that the international community should send a clear message to Pyongyang, according to Yonhap.

Seoul's foreign ministry said informal discussions on the issue have been underway among 15 members of the Council, including five veto-wielding permanent members.

Pyongyang also made its own case at the Council, claiming Seoul fabricated the findings of investigations led by a multinational team of investigators.