North and South Korea will march jointly under one unified flag during the opening ceremony of the Winter Olympics, the biggest sign yet of a detente after months of tensions over Kim Jong Un’s nuclear program.

The statement, made on Wednesday following the third round of talks in just over a week, said the two Koreas will form a joint women’s ice hockey team. They will also conduct some activities in North Korea, including a joint cultural event at Mount Geumgang and training for skiers from both countries at the Masikryong ski resort on the east coast.

It will be the first time the two Koreas have marched together during the opening ceremony of an international sporting event since 2007, and the ninth time overall, according to South Korea. The two Koreas haven’t competed under a single banner since 1991.

The progress came as U.S. Secretary of State Rex Tillerson warned about the possibility of war, telling fellow top diplomats in Canada that North Korea’s nuclear advancements had brought the world to a “tenuous stage.” President Donald Trump’s administration is seeking to maintain maximum pressure on North Korea even as Seoul reaches out to make the Olympics a success.

In an interview with Reuters later Wednesday, Trump said he hoped the standoff with Pyongyang could be resolved “in a peaceful way, but it’s very possible that it can’t.”

Tillerson Warns Threat of North Korea War Growing Despite Talks

North Korea’s athletes will come to South Korea on Feb. 1, with the rest of the delegation arriving on Feb. 7, according to South Korea. Pyongyang will also send 150 people, including athletes, a cheering squad, reporters and an art troupe to the Paralympics in March.

The sides have yet to decide who will represent Kim at the Games to be held in the ski resort of Pyeongchang from Feb. 9. Last week, they agreed to allow a 140-member North Korean orchestra to perform concerts in Seoul and Gangneung, a vacation city near Pyeongchang.

At an International Olympic Committee meeting in Switzerland planned for the weekend, officials will decide on matters such as the number and names of North Korean athletes and Olympic officials, the committee said in a statement last week. It will also decide on participation protocol regarding the flag that North Korea will compete under, as well as other matters concerning the anthem, ceremonies and uniforms.

In a sign that the Olympics may only be a temporary break from Kim’s threats and push to develop nuclear weapons capable of hitting America, a North Korean state-run newspaper called on South Korea to stop its military drills with the U.S.