The US and South Korea stand united against North Korea's nuclear program, even as the two Koreas hold talks in conjunction with the Winter Olympics, US Vice President Mike Pence said Saturday.

Analysts say the North's Olympic diplomatic drive seeks to loosen international sanctions against it and undermine the alliance between Seoul and Washington.

Pence, speaking to reporters aboard Air Force Two after attending the opening ceremony of the Games in Pyeongchang, South Korea, said that he and President Moon Jae-in "continue to stand strong" and coordinate efforts against the North.

"There is no daylight between the United States, the Republic of Korea and Japan on the need to continue to isolate North Korea economically and diplomatically until they abandon their nuclear and ballistic missile program," Pence said as he flew back to the United States.

Washington calls it a campaign of "maximum pressure."

But as tensions rose between the North and Washington, the Games triggered a rapid reconciliation between the two Koreas, who are still technically at war.

Moon was invited to a summit with Kim, even as the US warned against falling for Pyongyang's Olympic charm offensive.

The invitation was issued through Kim's sister, Kim Yo Jong, who was attending the Games with the North's ceremonial head of state Kim Yong Nam.

Washington insists that Pyongyang -- which is under multiple sets of United Nations Security Council sanctions -- must take concrete steps toward denuclearization before any negotiations can take place.

North Korea's delegation, the highest-ranking to visit the South and led by the younger sister of the North's leader Kim Jong Un, concluded its visit yesterday after charming and intriguing the South Korean public, but still faces deep scepticism over Pyongyang's sincerity towards improving relations.