The Trump administration dropped its consideration of plans to send U.S. military forces to the Canadian border to help with efforts to combat the new coronavirus, a U.S. official said Thursday, disclosing that decision after Canadian officials had strenuously objected to the idea.

Canadian Deputy Prime Minister Chrystia Freeland told reporters in Ottawa that officials there were told of the U.S. proposal a few days ago but wouldn’t disclose where the U.S. units might have gone or what they would do.

“We...