Outgoing Dutch Prime Minister Mark Rutte will be NATO's next secretary-general after being selected Wednesday as the successor of Jens Stoltenberg who will leave the position in October following a decade at the helm of the world's largest military alliance.

But with challenges ranging from the war in Ukraine to uncertainty about Washington's position in the alliance and growing tensions with China, the future NATO chief will have his work cut out for him as he takes the reins at a critical juncture for the organization.

“The alliance is and will remain the cornerstone of our collective security,” Rutte said after being appointed following a meeting of the 32-member organization, only days ahead of a key NATO leaders' summit in Washington that will also mark the alliance’s 75th anniversary.