Outgoing Dutch prime minister, Mark Rutte, has been formally selected as the next NATO secretary general, the military alliance announced on Wednesday, June 26.

His appointment comes after Romanian President Klaus Iohannis – his only rival for the position announced last week that he had withdrawn from the running.

Rutte is set to start his new position on October 1 when incumbent NATO chief Jens Stoltenberg’s 10-year tenure comes to an end, according to a statement from the alliance.

“It is a tremendous honour to be appointed Secretary-General of NATO. The Alliance is and will remain the cornerstone of our collective security,” Rutte said in a post on X Wednesday.

The Dutch PM, 57, said he was grateful to the NATO allies for placing their trust in him. “Leading this organization is a responsibility I do not take lightly,” he said.

Stoltenberg said Wednesday that he “warmly welcomes” the appointment of his successor.

“Mark is a true transatlanticist, a strong leader and a consensus-builder. I wish him every success as we continue to strengthen NATO,” he posted on X.

Ukrainian President Volodymyr Zelensky also took to X to congratulate the next NATO chief. “I know Mark Rutte as a principled and strong leader, who has demonstrated his decisiveness and vision on many occasions over the past years,” Zelensky said.

“When Mr. Rutte takes over this post from @JensStoltenberg in October, we anticipate that our joint work to ensure the protection of people and freedom throughout our entire Euro-Atlantic community will continue at good pace.”

Rutte will inherit a NATO that is supporting Ukraine’s defense against Russia’s invasion as it navigates the deadliest war on European soil in since World War II.