STOCKHOLM (Reuters) - North Korean vice foreign minister Choe Son Hui has arrived in Sweden to take part in roundtable talks, Sweden’s foreign ministry said on Friday, amid stepped up international efforts to end the stand-off between the United States and North Korea.

“The Ministry of Foreign Affairs can confirm that Choe Son Hui has arrived in Sweden to take part in roundtable talks in a smaller format together with international experts,” a Swedish foreign ministry spokesman said.

A diplomatic source said the purpose of the meeting was to take steps forward in the relations between U.S. and North Korea after things “ground to a halt” following a landmark meeting between U.S. President Donald Trump and North Korean leader Kim Jong Un in Singapore last year.

The source said earlier the talks had begun and had included Stephen Biegun, the U.S. special representative for North Korea. But a State Department official said Biegun was part of meetings with U.S. Secretary of State Mike Pompeo and North Korea’s lead negotiator, Kim Yong Chol, in Washington on Friday.

Kim Yong Chol’s visit is aimed at clearing the way for a second U.S.-North Korea summit and mark a rare sign of potential movement in a denuclearization effort that has stalled since the Singapore meeting.

The Swedish foreign ministry spokesman declined to say whether Biegun would be joining the talks in Sweden or whether the discussions had already begun.

The meeting, which is due to last over the weekend, has been planned in secret for months.

Sweden’s Foreign Minister Margot Wallstrom, Cabinet Secretary Annika Soder and Sweden’s envoy to Korea, Kent Harstedt, are also sitting in on the talks, the source said.

Trump and Kim met in Singapore in June last year for talks aimed at finding a way to end a nuclear standoff on the Korean peninsula.

Earlier this month, Trump defended the stuttering progress on North Korea by saying that Pyongyang had stopped missile and bomb testing and if it had not been for his administration “you’d be having a nice, big, fat war in Asia.”