An NFL spokesperson declined to address President Donald Trump’s latest tweet on Tuesday, which called for the league to create a rule that mandates players stand for the national anthem.

“I am little behind on his tweets,” NFL spokesperson Joe Lockhart told reporters on Tuesday. “I may catch up by the end of the day.”

Around 9 a.m. ET, Trump tweeted: "The NFL has all sorts of rules and regulations. The only way out for them is to set a rule that you can't kneel during our National Anthem!"

Earlier on Tuesday morning, Trump was tweeting about the Cowboys' protest on Monday night, as well as NFL ratings. The Cowboys and owner Jerry Jones took a knee before the national anthem played for a Monday Night Football matchup against the Cardinals in Arizona.

The Cowboys' gesture took place after a Sunday of protests throughout the NFL.

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Asked again about Trump calling for a rule change, Lockhart -- on a conference call where he highlighted the NFL’s “Unity” message in response to the protests -- didn’t engage.

“I guess I’d say he’s exercising his freedom to speak, and I’m exercising my freedom not to react,” Lockhart said.

NFL spokesman Brian McCarthy said that the policy regarding the anthem has been in place for several years, pre-dating protests that began during the 2016 season.

"It’s policy, it’s not a rule. I think where people are getting confused is, rules, that’s like holding or defensive pass interference, that’s a rule. This is policy," McCarthy said.

Trump's 2020 re-election campaign is using the anthem issue as part of a fundraising effort. Emails went out Monday night that read, "the President has asked if you stand with him."

Allison Carter of The Indianapolis Star contributed to this report.

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