U.S. Vice President Mike Pence was scheduled to meet with North Korean officials, including leader Kim Jong Un's sister, while in South Korea for the Winter Olympics this month but the North Koreans cancelled at the last minute, U.S. officials said on Tuesday.

"North Korea dangled a meeting in hopes of the Vice President softening his message, which would have ceded the world stage for their propaganda during the Olympics," Pence's chief of staff, Nick Ayers, said in a statement.

But after Pence condemned North Korean human rights abuses and announced plans for new economic sanctions, "they walked away from a meeting or perhaps they were never sincere about sitting down," Ayers said.

Pence was going to meet with North Korean leader Kim Jong Un's younger sister, Kim Yo Jong, and the nominal head of state, Kim Jong Nam, but the North Koreans called off the Feb 10 meeting two hours before it was set to start, a U.S. official said, confirming a story first reported by the Washington Post.

The encounter would have been the first scheduled between senior officials from the Trump administration and Pyongyang, which are in a standoff over the North's development of nuclear weapons capable of hitting the United States.

"The President made a decision that if they wanted to talk, we would deliver our uncompromising message. If they asked for a meeting, we would meet. He also made clear that until they agreed to complete denuclearisation we weren’t going to change any of our positions or negotiate," Ayers said, echoing comments made by Pence since he left the Olympics and other U.S. officials.

"This administration will stand in the way of Kim’s desire to whitewash their murderous regime with nice photo ops at the Olympics. Perhaps that’s why they walked away from a meeting or perhaps they were never sincere about sitting down," Ayers said in the statement.

South Korea's presidential Blue House said it had nothing to say on the matter.

Pence had criticized Pyongyang's nuclear ambitions and announced the "toughest and most aggressive" sanctions against Pyongyang yet, while also moving to strengthen the U.S. alliance with Japan and South Korea.

Kim Jong Un, through his sister, invited South Korean President Moon Jae-in to Pyongyang to begin talks “soon.”

READ: Kim Jong-un invites South Korean president for summit - South Korea

South Korea's Foreign Minister Kang Kyung-hwa told lawmakers on Wednesday that talks to improve inter-Korean relations had to go in hand with those linked to denuclearisation of the North. Seoul was in close talks and cooperation with Washington regarding engagements with Pyongyang, the minister said.

"Only when denuclearisation moves forward can inter-Korean relations move forward," said Kang, adding Washington's role is "very important" in bringing North Korea to abandon its nuclear ambitions.

Signs of a North-South thaw have prompted speculation that it could lead to direct talks between Washington and Pyongyang after months of tension and exchanges of insults between U.S. President Donald Trump and Kim, fuelling fears of war.

North Korea has refrained from carrying out any weapons tests since late November, when it shot off its largest intercontinental ballistic missile. South Korea's Unification Ministry declined to say on Wednesday whether North Korea has been engaging in its regular winter military exercises, which usually run from December for a few months.