Mike Pence, the US vice president, said he deliberately "ignored" the sister of Kim Jong-un at the Winter Olympics in South Korea.
Mr Pence, who was shown sitting just a few feet from Kim Yo-jong at the opening ceremony, said it would not have been proper for him to acknowledge her.
He said: "I did not. I didn’t avoid her but I did ignore her. I didn’t believe it was proper for the United States of America to give any attention in that form to someone who is not merely the sister of a dictator but the leader of a propaganda unit."
He said people should remember the assassination of Kim Jong-Nam, Kim Yo-jong’s half brother who was killed with chemical weapons at Kuala Lumpur airport.
Mr Pence added: "This is a regime and a family that also ordered that their uncle be executed with artillery fire in front of 10,0000 people, and she is the leader of the propaganda unit of that regime. This is evil the likes of which we have witnessed rarely."
Kim Jong-un’s family tree
The vice president said he had wanted to send a message with his silence.
In wide-ranging comments during a public interview conducted by Axios, Mr Pence also said the US was open to talks with North Korea, but "talks" did not mean "negotiations".
He said the US would continue to intensify diplomatic and economic pressure on North Korea over its nuclear ambitions, but that sanctions would not be lifted until its nuclear programme was abandoned.
Mr Pence also said the White House could have "handled better" a controversy over Rob Porter, the staff secretary who resigned after being accused of domestic abuse.
Winter Olympics 2018 opening ceremony: in pictures
The row engulfed the White House in recent days and undermined the standing of John Kelly, the chief of staff.
Mr Pence said he had "great confidence" in Mr Kelly. He added: "He has done a remarkable job as chief of staff and I look forward to continuing to work with him for many, many months to come."
He said the Trump administration and the US intelligence community were discussing plans to prevent Russia from interfering in future elections.
Mr Pence said: "We have discussed plans going forward to ensure that meddling in our elections by Russian or other powers around the world will be rebutted."