Shelby Houlihan will not be running at U.S. Olympic trials after all and will likely miss the 2021 Games altogether.

The U.S. Olympic and Paralympic Committee (USOPC) reversed a decision from USA Track and Field (USATF) on Thursday and decided to bar Houlihan from competing at the trials this weekend.

The USOPC told USA Today in a statement it would adhere to the decision made by the Court of Arbitration for Sport to prohibit Houlihan from running.

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The USATF said earlier Thursday it would allow Houlihan to run while she appeals a four-year ban for failing a drug test.

"Given there is an active appeal process, USATF will allow any athletes to continue competing until the process is completed," USATF director of communications Susan Hazzard said.

The organization said it did not want to bar Houlihan from potentially competing in Tokyo Olympics next month should her ban be overturned.

"You can always resolve the outcome later, but you can’t re-run a race," USATF CEO Max Siegel said.

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The USOPC said it decided to reverse the decision "together with the USATF."

Houlihan said earlier in the week the Court for Arbitration of Sport upheld her ban after testing positive for trace amounts of nandrolone, which is considered to be a performance-enhancing drug. Houlihan has contended she ate a pork burrito that contained the nandrolone before her test in December.

The next option for Houlihan could be to appeal to Switzerland’s highest court to overturn. That court can issue an injunction that would allow Houlihan to participate while the case is determined.

Houlihan starred at Arizona State and was a 12-time Division I All-American. She won a gold medal at the 2014 NACAC U23 Championships in Athletics and a silver in the 2018 Continental Cup.

She set her record in the 1,500-meter at the world championships in Doha, Qatar, in October 2019 with a time of 3 minutes, 54.99 seconds. She broke the U.S. 5,000-meter mark with a time of 14:23.92 in Portland, Oregon, in July 2020.

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She represented the U.S. in the 2016 Rio Games and finished in 11th place in the 5,000 meters.

The Associated Press contributed to this report.