South Korean women's ice hockey team members leave after attending an inaugural ceremony ahead of the 2018 Pyeongchang Winter Olympics, in Seoul, South Korea, Jan. 24, 2018.
South Korean women's ice hockey team members leave after attending an inaugural ceremony ahead of the 2018 Pyeongchang Winter Olympics, in Seoul, South Korea, Jan. 24, 2018.

SEOUL, SOUTH KOREA - A delegation of North Korean officials and ice hockey players crossed the heavily guarded border into South Korea on Thursday for joint Olympics training, as Pyongyang called for all Koreans to seek unification of the two nations.

The delegation included 12 North Korean players who will form a combined women's ice hockey team with their southern counterparts at next month's Winter Olympics in the South Korean mountain resort of Pyeongchang.

Under an agreement worked out during the first official talks between the two Koreas in two years, the joint team will wear unity jerseys and march under a unified peninsula flag at the games' opening ceremony February 9.

Earlier on Thursday, North Korea sent a rare announcement addressed to "all Koreans at home and abroad," saying they should make a "breakthrough" for unification without the help of other countries, its state media said.

All Koreans should "promote contact, travel, cooperation between North and South Korea," it said, adding that Pyongyang would "smash" all challenges against reunification of the Korean Peninsula.

The announcement, issued after a joint meeting of government and political parties, added Koreans should try to ease military tensions and create a peaceful climate on the Korean Peninsula.

North and South Korea remain technically at war after their 1950-53 conflict ended in a truce rather than a peace treaty. Tensions escalated dramatically last year as the regime of Kim Jong Un stepped up its program aimed at developing a missile capable of striking the United States with a nuclear warhead.

FILE - South Korean women's ice hockey goaltender
FILE - South Korean women's ice hockey goaltender So Jung Shin has the Olympic rings painted on her helmet, ahead of the South Korea Winter Olympics, during practice in Hamden, Conn., Dec. 27, 2017.

?Peace or propaganda?

Some South Korean opposition politicians and conservatives have criticized Pyongyang's participation in the Pyeongchang Games, saying Kim was using North Korea's involvement for his own purposes.

Many other South Koreans welcomed the North's participation, but complained that the unified women's ice hockey team — the only such joint team to be formed — was unfair to the players.

U.S. Vice President Mike Pence plans to use his attendance at the Winter Olympics in South Korea next month to try to counter what he sees as Kim's efforts to "hijack" the games with a propaganda campaign, a White House official said Tuesday.

Washington has been driving a tightening of sanctions on isolated North Korea. On Wednesday, it imposed fresh sanctions on nine entities, 16 people and six North Korean ships it accused of helping the weapons programs. It also urged China and Russia, North Korea's main allies, to expel North Koreans raising funds for the programs.

The South Korean government has rejected criticism that the games had been hijacked by North Korea, saying the event would help defuse tensions over Pyongyang's nuclear and missile programs.

Military tension on the Korean Peninsula was a "fundamental obstacle" for the improvement of inter-Korean relations and unification, the North's official news agency said in its statement Thursday.

It added that joint military drills with "outside forces" had shown to be unhelpful for the development of relations between North and South Korea.

South Korea successfully pressed the United States to delay large-scale annual drills involving the two countries' troops until after the Olympics, but Washington officials have rejected the idea of a permanent end to the exercises in exchange for North Korea's freezing of its missile and nuclear weapons tests.