NEW YORK — President Trump tweeted his disapproval of the NFL on Sunday morning before the first full slate of games. The president has criticized players for their demonstrations protesting social injustice during the national anthem, as well as the league for not requiring players be on the sideline while "The Star-Spangled Banner" is played.

He made reference to lower ratings on NBC in Thursday night's season opener, in which Super Bowl champion Philadelphia Eagles defeated the Atlanta Falcons 18-12.

"Wow, NFL first game ratings are way down over an already really bad last year comparison," Mr. Trump tweeted. "Viewership declined 13%, the lowest in over a decade. If the players stood proudly for our Flag and Anthem, and it is all shown on broadcast, maybe ratings could come back? Otherwise worse!"

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The protests were popularized by former San Francisco 49ers quarterback Colin Kaepernick, who recently became one of the faces of Nike's signature "Just Do It" campaign. Mr. Trump has also criticized Nike for featuring Kaepernick.

The NFL unilaterally passed a policy requiring players to stand at attention for the anthem or to stay in the locker room or in the tunnel under the stands. When that policy met with heavy criticism, it was put on hold while the league and players' association discussed other options. Those discussions are continuing.