NATO Secretary-General Jens Stoltenberg has officially passed leadership to former Dutch Prime Minister Mark Rutte after serving 10 years in the position. Rutte assumes the role at a pivotal time for the alliance.

Former Dutch Prime Minister Mark Rutte has officially assumed the role of NATO's secretary-general following a handover ceremony in Brussels.

He succeeds Norway's Jens Stoltenberg, who had been at the helm of the alliance since 2014.

After a symbolic handshake and the laying of a wreath at NATO's headquarters, the two leaders proceeded to a meeting with NATO ambassadors at the North Atlantic Council, marking Rutte's formal appointment.

The outgoing secretary-general expressed confidence in his successor, stating that the alliance was in "safe hands" with Rutte.

Rutte expressed gratitude to NATO allies for their confidence in him, acknowledging the magnitude of the responsibility. "It is a big job, and I have big shoes to fill," he remarked.

Stoltenberg's leadership began in the same year that Russia annexed Crimea. His time in office is only surpassed by Dutch diplomat Joseph Luns, who led NATO for 12 years.

In his first press conference as secretary-general, Rutte urged allies to "significantly increase defense spending" to address NATO's evolving challenges.

He emphasized that resolving the conflict in Ukraine is "vital for peace and security in Europe," adding that the cost of allowing Russian President Vladimir Putin to succeed would far exceed the price of providing aid to Kyiv.

Rutte also highlighted the importance of "enhancing cooperation with our Indo-Pacific partners," pointing to China's support of Putin and its role as a destabilizing force globally.

Rutte, who served as Dutch prime minister for a long time, takes over as NATO's leader as Russia's invasion of Ukraine nears its 1,000-day mark.

With Russian forces continuing to make gains in eastern Ukraine, a key aspect of Rutte's role will be maintaining Western support for Kyiv, especially as fatigue over the prolonged conflict sets in.

On Tuesday, Rutte emphasized that Ukraine remains "on top of our list," along with keeping an eye on the unfolding situation in Lebanon.

Another concern for NATO members is the upcoming US presidential election in November. As the US is NATO's most powerful member, a win by former President Donald Trump could potentially unsettle the alliance, as it did during his first term, when he pressured allies to boost defense spending and questioned the bloc's core principle of collective defense.

Nonetheless, Rutte downplayed these concerns during the handover, stating, "I'm not worried. I know both candidates very well. I worked for four years with Donald Trump," referencing his time as the Dutch prime minister.