In this image captured from Youtube, Sydney Seiler, national intelligence officer for North Korea at the Office of the Director of National Intelligence, speaks in a webinar hosted by the Washington-based Center for Strategic and International Studies (CSIS) think tank, Sept. 29.

The top U.S. intelligence officer on North Korea on Wednesday argued the North does not seek a permanently improved relationship with South Korea, arguing the North's long-term objective remains decoupling the U.S.-South Korea alliance and possibly invade South Korea.

"I'm always interested to see an introduction of a new piece of intelligence or information that would overturn my assessment but you just have to conclude strategically North Korea does not seek sustained improved relations with South Korea," said Sydney Seiler, national intelligence officer for North Korea at the Office of the Director of National Intelligence.

"In fact, you can make more arguments because of influence, cultural influence, political influence and the price that would have to be paid. There's no real sustained North-South daytime without the nuclear issue being addressed that just the cost of sustained engagement with the South is greater than it's worth for the North," he added in a webinar hosted by the Washington-based Center for Strategic and International Studies think tank.

His remark comes after North Korean leader Kim Jong-un's sister, Kim Yo-jong, said the two Koreas may discuss ways to improve inter-Korean relations and even hold an inter-Korean summit if Seoul dropped its hostility against her country.

North Korean ambassador to the U.N., Kim Song, on the other hand, called for a permanent end to the joint military exercises of South Korean forces and U.S. Forces Korea (USFK) troops, calling them a sheer example of what he called the countries' hostility against the North.

Seiler said the North has always tried to and continues to seek to drive a wedge between the two allies.

"I think North Korea is well aware of the strength of the alliance and this is a value of, first of all, 28,500 (U.S. Forces Korea) troops on the ground with dependence. So the commitment of the United States to the defense of Republic of Korea is well understood by North Korea," he said.

"That's why the North Koreans hate our exercises. Not because they feel our exercises are a threat, but (because) they are a regular reminder ― our training and our exercises ― that we have an alliance that is committed to deny North Korea from seeking to do what it attempted to do on June 25, 1950 and what it has attempted to generate year after year," he added, referring to the start date of the 1950-53 Korean War.

The U.S. official reiterated the allies must not ease their joint deterrence or their emphasis on the denuclearization of the Korean Peninsula as the North Korean leader may come to believe that "first, he can gain acceptance as a nuclear weapons state" and "second, split the U.S.-ROK alliance ― achieve decoupling."

Seiler also insisted the countries should not pay too much attention to North Korean provocations such as missile launches, noting they only indicate the North's continued to efforts to improve its weapons systems.

North Korea on Wednesday (Seoul time) said it test fired a new hypersonic missile the previous day.

"All too often, however, people are overly focused on when's the next launch or when's the next talks. We know talks will come. We know launches will come ... The longer term strategic implications of a non-denuclearizing North Korea is where everybody's eyes and minds and heads should be focused right now," he said.

To prevent North Korea from achieving its "longer term strategic objectives," Seiler said they countries must seek to establish an international consensus that the North will never be accepted as a nuclear weapons state.

"Maintaining that international consensus on the unacceptability will send a strong message to Pyongyang that their strategy is not working," he said.

"The opposite is frankly potentially dangerous because it could encourage Kim Jong-un beyond the mere possession of nuclear weapons but using those to achieve longer term strategic objectives we all know," added Seiler. (Yonhap)