The outreach, directed by the Pentagon leadership, came after Trump threatened to reassess those commitments during a gathering with NATO allies in Brussels, according to multiple current and former diplomatic and military officials familiar with the calls.

The overall message from senior military officials in a series of phone calls to members of the North Atlantic Treaty Organization has been that U.S. military bases in their countries will remain open and American troop levels in the region will not be reduced.

The Pentagon-led effort was meant to counter Trump’s withering criticism about the security alliance that rattled European leaders.

“One thing you need in this alliance is predictability,” one diplomatic official said.