A group of veterans will ask Sen. John McCain and other Republican leaders on Thursday to un-endorse Donald Trump following his criticism of a Gold Star family.

Perry O'Brien, a veteran of Operation Enduring Freedom in Afghanistan, will lead the group to deliver a petition with more than 50,000 signatures to the offices of congressional Republicans asking them to withdraw their support for the GOP nominee over his "unrelenting attack" on the family of Capt. Humayun Khan, a Muslim soldier who was killed in Iraq.

"I'm appalled at Trump's disrespect for military families and his use of veterans as political props," O'Brien wrote on the petition. "If Republican leaders do not outright disavow Trump's dangerous rhetoric, they are not only endorsing Donald Trump's candidacy, but also his attacks on veterans."

O'Brien is the founder of Common Defense, an organization that is based on a "shared belief that Donald Trump is unfit to be our next commander-in-chief."

They will deliver the petition to McCain, a veteran himself, as well as Senate Majority Leader Mitch McConnell and House Speaker Paul Ryan.

Trump recently faced criticism for his comments about the Khan's parents, who spoke at the Democratic National Convention. Trump first made waves by suggesting that Khan's mother, who joined her husband on stage, was not allowed to speak during the convention, but escalated the conflict over a series of days.

"Mr. Khan, who does not know me, viciously attacked me from the stage of the DNC and is now all over T.V. doing the same - Nice!" Trump tweeted.

Many Gold Star families publicly took issue with the remarks, saying that an attack on one was an attack on all who lose a loved one in the military.

Several lawmakers also released statements condemning the remarks, with McCain's specifically naming the GOP nominee.

"In recent days, Donald Trump disparaged a fallen soldier's parents. He has suggested that the likes of their son should not be allowed in the United States — to say nothing of entering its service," the Arizona senator said in a statement released by his office Monday. "I cannot emphasize enough how deeply I disagree with Mr. Trump's statement. I hope Americans understand that the remarks do not represent the views of our Republican Party, its officers, or candidates."

Trump announced on Tuesday that he would likely not endorse McCain or Ryan in their primaries.