"(The new Korean president) should promptly visit the United States before the summer, when the Washington administration sets up the Asia-Pacific strategy," said An, who is affiliated with the main opposition Democratic Party.

He was replying to a question, which country the next president should visit first between the United States and China, amid growing rifts over the planned deployment of a US missile shield in South Korea.

His rival Moon Jae-in was lambasted by conservatives after he said recenlty he would visit North Korea earlier than the United States.

"China is also our longtime friend that we should maintain a close relationship with. Behavior which appears slanted in position in diplomatic protocol poses a grave danger," An said.

An has recently soared in presidential polls and currently trails front-runner Moon. Both were close aides to late former President Roh Moo-hyun.

He has veered from his party's opposition to the deployment of the Terminal High Altitude Area Defense system, saying that the agreement between the two nations could not be easily rescinded by the next administration in Seoul.

During the forum, An defended his position saying that national security issues should not be affected by volatile electoral politics.

"While pushing ahead toward a self-reliant defense in the strategic frame of the Korea-US alliance, we should not disregard the US' status in the Asia-Pacific region," he said.

Regarding North Korea, he underscored a strategic blending of diplomacy and pressure.

He said Seoul should aim at a peaceful resolution of inter-Korean disputes, including the resumption of the suspended joint industrial complex in Kaesong. But the South should join international sanctions on the North if it continues to engage in provocative actions, he added. (Yonhap)