President Trump returned to Twitter on Monday night to continue his four-day campaign against NFL players taking a knee during the national anthem, claiming there has been a “tremendous backlash” following Sunday's widespread show of solidarity on the sidelines by players, coaches and some team owners.

In one of a new series of tweets, Trump criticized players for “disrespect of our Country.” Monday night's output followed a similar set of tweets on Monday morning, during which Trump praised football fans who booed NFL players taking a knee during the national anthem on Sunday.

“These are fans who demand respect for our Flag!” Trump said, also asserting that only a “small percentage” of players knelt.

The president also praised NASCAR supporters and fans, saying they were with him, and denied that his stance has anything to do with race.

“It is about respect for our Country, Flag and National Anthem. NFL must respect this!” Trump said in another tweet.

His comments followed a remarkable Sunday during which players at games across the country locked arms, knelt or stayed in the locker room during the anthem in a show of solidarity. Several team owners also participated.

U.S. athletes have a long history of protesting during the national anthem. Here is how some competitors have used their platform to protest. (Taylor Turner, Amber Ferguson/The Washington Post)

At a political rally in Alabama on Friday, Trump demanded that NFL owners “fire or suspend” players who kneel during the national anthem, using a profane term to describe players who do. He has also called for fans to boycott games if the form of protest continues.

In the first of his Monday tweets, Trump referenced the stance of several owners at a NASCAR event held in New Hampshire. They made clear that drivers and others could be fired if they don’t stand during the national anthem.

“So proud of NASCAR and its supporters and fans,” Trump said on Twitter. “They won't put up with disrespecting our Country or our Flag — they said it loud and clear!”

When he returned to Twitter on Monday night, Trump also took issue with a CNN report that said his chief of staff, John Kelly, was not pleased with Trump's fight with the NFL.

In a tweet, Trump said Kelly “totally agrees w/ my stance” and called CNN “Fake News.”

The network interviewed Kelly, who said he is "appalled” by what he sees as a lack of respect for the flag and national anthem. But CNN said Kelly declined to comment about Trump's decision to press the issue as he has in recent days.