NATO Secretary General Jens Stoltenberg speaks during a press conference after a NATO defense ministers meeting at NATO headquarters in Brussels, Belgium, on June 27, 2019. The two-day NATO defense ministers meeting closed on Thursday. (Xinhua/Zhang Cheng)

US Acting Secretary of Defense Mark Esper attends a press conference after a NATO defense ministers meeting at NATO headquarters in Brussels, Belgium, on June 27, 2019. The two-day NATO defense ministers meeting closed on Thursday. (Xinhua/Zhang Cheng)

US Acting Secretary of Defense Mark Esper (L) chats with Turkish Defense Minister Hulusi Akar while attending a NATO defense ministers meeting at NATO headquarters in Brussels, Belgium, on June 27, 2019. The two-day NATO defense ministers meeting closed on Thursday. (Xinhua/Zhang Cheng)

Canadian Defense Minister Harjit Singh Sajjan (R) attends a NATO defense ministers meeting at NATO headquarters in Brussels, Belgium, on June 27, 2019. The two-day NATO defense ministers meeting closed on Thursday. (Xinhua/Zhang Cheng)

British Defense Secretary Penny Mordaunt (2nd R) attends a NATO defense ministers meeting at NATO headquarters in Brussels, Belgium, on June 27, 2019. The two-day NATO defense ministers meeting closed on Thursday. (Xinhua/Zhang Cheng)

A NATO defense ministers meeting is held at NATO headquarters in Brussels, Belgium, June 27, 2019. The two-day NATO defense ministers meeting closed on Thursday. (Xinhua/Zhang Cheng)