"European allies and Canada can of course do more, but it's extremely important that the United States continues to provide support to Ukraine," the head of the Western military told AFP on the sidelines of a European summit in Britain.

"This has to be a joint effort between North America and Europe, and the United States is by far the biggest ally. So, I expect them to continue to support Ukraine."

Trump -- who is challenging incumbent Joe Biden at elections in November -- set alarm bells ringing across Europe this week by selecting J.D. Vance as his pick for vice president.

Vance is a staunch opponent of aid for Kyiv, and fiercely argued against the approval of $61 billion in new US military aid for Ukraine earlier this year.

Stoltenberg insisted that "it is in the security interest of the United States to support Ukraine".

"If President Putin wins in Ukraine, it will not only be a tragedy for the Ukrainians, it will also make the world even more dangerous and more vulnerable," he said.

The United States has provided tens of billions of dollars in military assistance for Kyiv since Russian President Vladimir Putin launched a full-scale invasion of Ukraine in February 2022.

But Vance and other Trump allies in Congress argue that Washington cannot continue to fund the war indefinitely, and a Trump victory would throw future US assistance for Ukraine into doubt.

Trump has said he would quickly end the conflict, raising the spectre that Kyiv could be pushed to negotiate with Moscow from an unfavourable position.

"If we really want to negotiate a solution where Ukraine prevails as a sovereign, independent nation, the way to get there is to provide more support to Ukraine," Stoltenberg said.

"Now, President Putin believes that he can win on the battlefield, and we need to convince him that he will not win on the battlefield -- that's when he will be willing to sit down and agree a solution."

Concerned about potential political changes in the US, NATO decided, at a summit last week in Washington, that the alliance would take over coordination of weapons deliveries to Ukraine from the United States.

Stoltenberg said that this will see a new NATO command overseeing some 700 personnel from across the alliance begin working in Germany in September.