BRUSSELS — Secretary of State Rex W. Tillerson joined on Friday a growing list of Trump administration officials to visit the hub of North Atlantic solidarity and scold the United States’ European allies, saying they do not spend enough on their collective defense.

“Allies must increase defense spending to meet their commitments,” Mr. Tillerson said, again and again, in a speech to NATO foreign ministers in Brussels.

Like Vice President Mike Pence and Defense Secretary Jim Mattis before him, Mr. Tillerson insisted that all 28 members of the alliance spend at least 2 percent of their gross domestic product on their military, a level only a handful of members meet.

Along with the familiar rebukes, Mr. Tillerson also sought to reassure Europe that the United States — despite comments from President Trump referring to NATO as “obsolete” — remains committed to an alliance that has kept the peace on most of the Continent for nearly 70 years.