US Vice-President Mike Pence has said his country and South Korea are in complete agreement on the need to maintain pressure on North Korea.
Speaking on his way home from the Winter Olympics in South Korea, Mr Pence said there was "no daylight" between the two allies on the issue.
The Games has seen better ties between the two Koreas despite tensions over the North's nuclear programme.
But the US has distanced itself from the North Korean overtures.
On Saturday North Korean leader Kim Jong-un invited the South's President, Moon Jae-in, to Pyongyang for talks.
It would be the first summit in more than a decade between Korean leaders. Mr Moon said the Koreas should "make it happen" and encouraged the North to return to negotiations with the US.
However, his Prime Minister, Lee Nak-yeon, said on Sunday he hoped "the right conditions" would be created for the summit to be held, with support from the international community. He did not specify what conditions he had in mind.
Pyongyang's nuclear programme is expected to hang over any attempts to bring the countries closer together.
The US administration has sought to maintain pressure on North Korea through sanctions and tough rhetoric from President Donald Trump.
Speaking to reporters during a flight on Saturday, Mr Pence said: "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 programme."
The handwritten invitation to President Moon was delivered by Mr Kim's influential sister, Kim Yo-jong, at a landmark meeting in the presidential palace in Seoul, as the Games opened on Saturday.
Ms Kim and the North's ceremonial head of state Kim Yong-nam made up the most senior delegation from the North to visit the South since the Korean War in the 1950s.