WASHINGTON — President Trump doubled down on his war with the Philadelphia Eagles on Tuesday, hosting a short celebration without the team as his spokeswoman accused the Super Bowl champions of turning their White House invitation into “a political stunt.”

Mr. Trump, his hand over his heart, sang along as the United States Marine Band and the Army Chorus performed the national anthem on the South Lawn. In brief remarks, Mr. Trump did not mention the Eagles as he urged Americans to always stand for the anthem.

“We love our country, we respect our flag and we always proudly stand for the national anthem,” Mr. Trump said. “We stand to honor our military and to honor our country and to remember the fallen heroes who never made it back home.”

The message from the president was clear: a denunciation of football players who knelt during the anthem or have said they would stay in the locker room when it is played — even though none of the Eagles players did either of those things during their winning season.