Jacksonville Jaguars owner Shad Khan believes President Donald Trump's failure to purchase the Buffalo Bills in 2014 has fueled his vendetta against the NFL.

"This is a very personal issue with him," Khan told USA Today Sports as he was leaving the NFL's fall meetings in New York.

Trump's history with the NFL goes back further than that, however. He led a failed effort to force a merger between the United States Football League (USFL) and the NFL. Trump, who owned the USFL's New Jersey Generals, pushed his fellow owners to shift the league's schedule from the spring to the fall and compete head-to-head with the NFL. That schedule shift was planned for 1986 but never happened. The USFL filed an antitrust lawsuit against the NFL in 1984, trying to force a merger or win a large settlement. The case went to trial in 1986 and the USFL was victorious, but was awarded only $3 and folded shortly afterward.

Khan told USA Today Sports that Trump's attacks are "about money, or messing with -- trying to soil a league or a brand that he's jealous of."

Trump has called for NFL owners to "fire" players who won't stand for the national anthem and has been openly critical of the league for not adopting a rule to make standing during "The Star-Spangled Banner" mandatory.

Commissioner Roger Goodell said Wednesday that owners believe players should stand for the national anthem but that the league wasn't changing its official policy. Instead, the NFL is focused on working with players to address the underlying issues behind their protests.

Trump continued his campaign against the NFL on Wednesday, tweeting in the morning and afternoon to express his disappointment with owners for not forcing players to stand.

The NFL has decided that it will not force players to stand for the playing of our National Anthem. Total disrespect for our great country! — Donald J. Trump (@realDonaldTrump) October 18, 2017

.@NFL: Too much talk, not enough action. Stand for the National Anthem. — Donald J. Trump (@realDonaldTrump) October 18, 2017

"He's been elected President, where maybe a great goal he had in life to own an NFL team is not very likely," Khan told USA Today Sports. "So to make it tougher, or to hurt the league, it's very calculated."