PYEONGCHANG, South Korea -- Vice President Mike Pence vowed Wednesday the U.S. will soon hit North Korea with the "toughest and most aggressive" sanctions yet over its nuclear weapons program. Pence is on his way to lead the U.S. delegation at the Winter Olympics in South Korea.

The younger sister of North Korean dictator Kim Jong Un is also heading to the Olympics. Kim Yo Jong is believed to be a trusted adviser to her brother, but it's not clear if she's being sent to deliver a message on his behalf.

"We'll look closely at who's with her and what she does and what she says," said North Korea expert Jeffrey Lewis. "But we don't have a lot of details about what precisely her role is."

Because of her influence, the South Korean media calls her the North's Ivanka Trump. She would be the first member of North Korea's ruling family to cross the border. But she may not receive a warm welcome.

Protesters have been greeting the members of the North's delegation, which numbers more than 500 people. They're angry that Kim Jong Un's regime is participating in the Olympics and stealing the spotlight.

South Korea has requested a waiver from the United Nations Security Council for North Korean sports official Choe Hwi to travel to the games, CBS News' Pamela Falk reports. Choe is on a U.N. blacklist barring him from travel. The Security Council has until Thursday to consider the request.

"We are working closely with the U.S. and others to ensure that there will be no violations of U.N. Security Council sanctions resolutions in regard to the visit by the high-level North Korea delegation," said Cho Tae-yul, South Korea's ambassador to the U.N.

Meanwhile, Pence is attending the opening ceremony to counter what he views as propaganda.

"We will not allow North Korean propaganda to hijack the message and imagery of the Olympic Games," Pence said.

At a stop in Tokyo, Pence announced new but unspecified sanctions on North Korea. They are expected to take effect during the games, which could complicate the efforts of South Korea to engage Kim Jong Un's regime. But experts say sending his sister is a sign of what Kim Jong Un is thinking.

"North Korea's government is a family affair. It's run by the Kim family. So to send a senior and important member to the Olympics means the government is taking this very seriously," said Lewis.

Members of North Korea's delegation are expected to meet with South Korean President Moon Jae-in while they are here. A meeting between them and Pence now seems less likely given the U.S. is about to impose more sanctions on North Korea.