(CNN) Sen. Tammy Duckworth called on her service as a veteran to express her support for National Anthem protesters in the wake of the NFL's new policy mandating players on the field stand for the song.

"One day, our nation's flag will drape my coffin, just as it did my dad's and will my husband's and brother's," the Illinois Democrat posted on Twitter and Facebook Friday, along with a photo of her prosthetic legs.

"I will always stand on these legs for the flag and anthem, but it was ALSO my honor to defend people's right to free speech—including those who choose to #TakeAKnee to express outrage at the glaring disparity in how Americans of different races are treated," she wrote.

Duckworth was serving in the US Army in Iraq in 2004 when her Black Hawk helicopter was hit by a rocket-propelled grenade. The attack resulted in the loss of both of her legs. She was awarded the Purple Heart for her injuries.

The senator's social media posts follow Wednesday's decision by the football league mandating that players stand for the National Anthem or stay in the locker room during the song. NFL Commissioner Roger Goodell said that teams whose players and personnel do not stand and show respect for the flag and the anthem will be fined by the league.

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