When military leaders from roughly 50 nations meet in Brussels on Friday to discuss aid shipments to Kyiv, one will be noticeably absent: Defense Secretary Pete Hegseth.

Instead of attending the gathering, the 27th meeting of the Ukraine Defense Contact Group, in person, Mr. Hegseth is expected to dial in and participate virtually.

It will be the first time since the group’s creation three years ago that the Pentagon’s top civilian will not be physically present for an in-person meeting of the group, as the Trump administration treats Ukraine less like a partner and moves closer to Russia.

President Trump promised on the campaign trail to settle the war between Russia and Ukraine even before he was sworn in, and said that he could do it within 24 hours. But cease-fire negotiations with Washington, Kyiv and Moscow have failed to yield an end to fighting that has led to the deaths of an estimated 100,000 Ukrainian and 150,000 Russian soldiers.

U.S. leadership of the contact group had provided a lifeline of arms and materiel for Ukraine’s armed forces, but the flow of goods has largely petered out since Mr. Trump’s second inauguration.

Ukraine particularly needs air-defense munitions, such as the Patriot missiles the United States previously shipped. That was brought into sharp focus last week when a Russian missile attack in central Ukraine struck near a playground, killing 19 civilians, including nine children.