Nick Symmonds is a six-time outdoor national champion at 800 meters. He finished fifth at the 2012 London Olympics in a personal best of 1 minute, 42.95 seconds. And he has been named to the U.S. team for the world track and field championships this month in Beijing.

Except Symmonds may not reach the starting line.

He is involved in a dispute with American track officials that has nothing to do with running or doping, but rather with corporate sponsorships.

Specifically, it is a conflict between an athlete’s personal endorsements and rules about uniforms and gear that must be worn while representing the national team at events like the world championships and the Olympics.

Symmonds said he refused to sign what he called a vague document that governs when athletes in Beijing must wear team gear made by Nike, the official sponsor of USA Track and Field. Symmonds is sponsored by another apparel company, Brooks.

If he does not sign the document by Sunday, when the American roster must be submitted to track’s world governing body, Symmonds “will not be on the team,” said Jill Geer, a spokeswoman for USATF.

Asked what he would do if USATF rescinded his place in the world championships, which begin Aug. 22, Symmonds said in a telephone interview Thursday night from Seattle, “I’d probably have to talk to a lawyer.”

The conflict, first reported by Sports Business Daily, reflects an ongoing tension in track and field. Many athletes have their own endorsement deals with apparel companies. The national federation has its own deal. Sometimes those collide.

Nike has signed an extension to sponsor USA Track and Field through 2040 for what has been estimated to be $20 million a year.

The question at the heart of the Symmonds apparel dispute is: What is an official team function?

The USATF document in question, known as a statement of conditions, is included in the federation’s bylaws. It stipulates that athletes agree to wear team gear at official functions while representing the United States.

According to the document, official team functions include competitions, awards ceremonies and news conferences. The document also mentions “other official team functions” that are not described in detail.

A separate letter that Symmonds said he received several weeks ago from the USATF seems to include broader language. It mentions team functions “at the athlete hotel” and “during training.” The letter also asks athletes to “pack only Team USA, Nike or non-branded apparel” for Beijing. The word “only” is uppercased and underlined in the letter.

The list of official gear includes uniforms, bandannas, headbands, hats, sweatbands, wristbands, socks, sports bras and travel bags, but it does not include sunglasses, watches and shoes, according to the USATF letter.

Geer, the USATF spokeswoman, said the document regulating official attire adhered to industry standards that govern international sports and professional leagues.

“It’s very common in all sports to have star athletes whose personal contracts conflict with their teams,” Geer said. “Steph Curry is with Under Armour and LeBron James is with Nike. Both men played in Adidas uniforms in the NBA finals last season.”

But Symmonds said the document that American athletes are being required to sign takes the commitment far beyond the playing field. He called it ambiguous and overreaching. “I can’t sign this,” Symmonds said. “It’s such a poorly worded document.”

Since signing with Brooks on Jan. 1, 2014, Symmonds, who was formerly sponsored by Nike, said he was asked by American officials to remove Brooks gear even while having morning coffee at the U.S. team’s hotel at the 2014 world indoor championships in Poland. Surely, coffee is not an official team function, Symmonds said.

The USATF “has confiscated advertising space that I own,” Symmonds, 31, said. He said the USATF “frequently uses bullying tactics to force athletes to do what they want, even when they have no legal right to do that.”

He said he would comply with regulations governing attire if they were clearly defined, adding, “I’m not for chaos.”

But Symmonds said the document he is being asked to sign seemed to violate his own contract with Brooks. “I deserve the right to know what an official team function is,” Symmonds said. “They haven’t defined that yet.”

Judging by the recent letter from the USATF, Symmonds said, the federation apparently wants him to wear Nike gear for the world championships from the time he leaves his apartment in Seattle.

“That’s absurd,” he said.

Geer said the federation strived to balance the interests of individual athletes with those of the governing body. The USATF spends $2.5 million yearly on televised meets that allowed athletes to wear whatever they wanted during competitions and news conferences so that they could maximize their endorsement potential, Geer said.

“The only time we limit what athletes can wear is when they are representing the United States,” Geer said.

Symmonds said he had not signed a statement of conditions before competing at the 2014 indoor worlds. The USATF disputed this, saying it has Symmonds’ electronic signature on file.

In a statement, Brooks said: “The conversation on athletes’ rights is worth having, as it has significant impact on their ability to pursue their dreams. Nick has carried that baton for years, and our support of him will continue regardless of his competition” at the world championships.

Asked if he would maintain the same position next year and potentially give up a chance to compete at the Olympics in Rio de Janeiro, Symmonds said: “It’s a really good question. I don’t know.”

He would first have to see the regulations governing attire, Symmonds said. “It’s hard to say until I cross that bridge, I guess.”