BRUSSELS (AP) — The new head of NATO vowed on Tuesday to help shore up Western support for war-ravaged Ukraine and expressed confidence that he can work with whoever is elected president of the United States, the alliance's most powerful member, in November.

“There can be no lasting security in Europe without a strong, independent Ukraine,” new NATO Secretary-General Mark Rutte said in his first speech on taking office, and he affirmed a commitment made by the organization’s leaders in 2008 that “Ukraine’s rightful place is in NATO.”

Russian President Vladimir Putin's forces are making advances in eastern Ukraine. Ukraine’s army has a shaky hold on part of the Kursk region in Russia, which has provided a temporary morale boost, but as casualties mount it remains outmanned and outgunned.

"The cost of supporting Ukraine is far, far lower than the cost we would face if we allow Putin to get his way,” Rutte told reporters, a few hours after his predecessor Jens Stoltenberg handed the reins to him, along with a Viking gavel with which to chair future meetings.

But Ukraine’s NATO membership remains a distant prospect. Several member countries, led by the U.S. and Germany, believe that Ukraine should not join while it’s fighting a war. Rutte declined to speculate about what must happen before it can stand among NATO's ranks.

Rutte did single out China, and particularly Beijing's support for Putin. “China has become a decisive enabler of Russia’s war in Ukraine. China cannot continue to fuel the largest conflict in Europe since the Second World War without this impacting its interests and reputation,” he said.

NATO's new top civilian official also underlined the importance of keeping the trans-Atlantic bond between the United States, Canada and Europe strong, with U.S. elections just a month away.

Surveys suggest the election will be a close race. It could see the return of Donald Trump, whose bluster during his last term of office about low defense spending among European allies and Canada undermined the trust of NATO member countries.

It became an existential challenge, as smaller members feared that the U.S. under Trump would renege on NATO’s security pledge that all countries must come to the rescue of any ally in trouble, the foundation stone the alliance is built on.

But Rutte said: “I know both candidates very well.” He praised Trump for pushing NATO allies to spend more and for toughening their approach toward China. He also hailed the “fantastic record” of Vice President Kamala Harris and described her as “a highly respected leader.”

“I will be able to work with both. Whatever is the outcome of the election,” Rutte said. When pressed about Trump's commitment to the other allies, he deflected, saying only that both candidates “understand that, in the end, the trans-Atlantic relationship is crucial, not just for Europe.”

Asked whether the Netherlands, which has only just reached NATO's spending of 2% of gross domestic product on its defense budget, has set a good example to other allies, Rutte shook his head and said “No. We should have done this earlier.”

Incumbent U.S. President Joe Biden said in a statement that the U.S. remains “deeply devoted” to the alliance, and expressed confidence that Rutte would “continue to build on our work to create a NATO that is stronger, larger, and more resolute than ever in its mission to create a safer world for our peoples.”

Earlier, Stoltenberg had welcomed Rutte to NATO headquarters in Brussels for the change of leadership.

The two men, who first sat together at NATO's table 14 years ago as the leaders of Norway and the Netherlands, greeted each other warmly, before laying a wreath to fallen military personnel, surrounded by the flags of the 32 member countries.

“Mark has the perfect background to become a great secretary general," a visibly emotional Stoltenberg said as he ended a decade in office.

"He has served as prime minister for 14 years and led four different coalition governments, so therefore he knows how to make compromises, create consensus, and these are skills which are very much valued here at NATO,” Stoltenberg said.

Rutte said that he "cannot wait to get to work.” Among his other priorities, he said, are to increase defense spending and strengthen partnerships that the alliance has established with other countries around the world, notably in Asia and the Middle East.

After hundreds of NATO staffers applauded the two men as they moved inside to the great hall where North Atlantic Council meetings are held at the level of ambassadors, ministers or leaders, Stoltenberg helped his successor to get started by presenting him with a Viking gavel to use when chairing meetings.

Stoltenberg, NATO’s 13th secretary-general, took over in 2014, the year that “little green men” from Russia infiltrated Ukraine. Moscow annexed the Crimean Peninsula, sparking a defense spending buildup at the world’s biggest security alliance that gathered pace over his term.

His tenure was surpassed only by Dutch diplomat Joseph Luns, who spent 12 years in charge of NATO.

NATO secretaries-general run the HQ, drive the alliance's working agenda and speak on behalf of the 32-nation organization with one unifying voice. Continuity is usually the key word when they take up office.