The American middle distance star Shelby Houlihan, who blames a contaminated burrito for a failed drugs test, is highly unlikely to run in the US Olympic trials this weekend despite initially being given permission to compete despite a four-year doping ban.

As first revealed by the Guardian on Thursday, USA Track and Field has faced intense pressure from multiple sports and anti-doping bodies to reverse its decision to allow Houlihan to compete in the 1500m and 5000m, even though for now she remains on the start lists.

Several sources said that Usatf has been told in no uncertain terms that it would be in breach of the World Anti-Doping Code if it allowed the 28-year-old to run after she was banned by the court of arbitration for sport following a positive test for the anabolic steroid nandrolone.

The US Olympic and Paralympic Committee chief executive Sarah Hirschland later appeared to confirm a U-turn was imminent, saying: “The US Olympic & Paralympic Committee, together with Usatf, can confirm that we will adhere to the Wada Code and any Cas decisions that govern athlete participation in sanctioned events.”

Earlier World Athletics had issued a terse statement that said: “All member federations must respect CAS decisions under the world anti-doping code. We are talking to Ustaf.”

Prior to Hirschland’s statement it was made clear to Usatf that if Houlihan competes on Friday she could face a further sanction under article 10 of the world anti-doping code. Usatf was also reminded that as a member of World Athletics it is bound by the code and the CAS ruling.

Pressure was also applied by the Athletics Integrity Unit, which wrote to Usatf to remind it that Houlihan was “strictly prohibited” from competing because of her four-year ban. “Ms Houlihan’s status during the period of Ineligibility means that participation in any Competition or activity authorised or organised by a World Athletics Member Federation, such as Usatf (i.e., the US Olympic Team Trials – Track & Field) is strictly prohibited,” it said in a statement.

The news that 28-year-old Houlihan had been included in the start list for Friday’s heats of the women’s 1500m and 5,000m in Eugene, Oregon, caused uproar throughout the sport. Initially, without naming Houlihan, Usatf had indicated its policy during an active appeal process was to “allow any athletes to continue competing until the process is completed.”

Speaking to Fox News on Wednesday, Houlihan said she was “trying to exhaust every option” to overturn the ban. “I worked really hard and I’m in the best shape of my life right now, but I’m trying to trust the process and hope that I can get justice from this,” she said.

Earlier in the week Houlihan, who ran 3:54.99 in finishing fourth at the 1500m world championships in 2019, said she had “never even heard of” nandrolone, which can help to increase muscle mass.

In a statement to the Guardian, the US Anti-Doping Agency confirmed it was currently illegal for Houlihan to run. “Despite how frustrated people might be with the Cas decision, she is serving a sanction. Under the rules she’s not allowed to compete. It would be illegal for her to do so, unless a court orders differently.”