Apple appears unwilling to take part in an upcoming hearing the Senate plans to hold on anti-competitive app store practices. In a letter spotted by Bloomberg that’s addressed to Apple CEO Tim Cook, Senators Amy Klobuchar and Mike Lee, the chair and leading Republican on the Senate Judiciary’s antitrust subcommittee, state the company abruptly declined to send a witness 16 days before the scheduled start of those hearings.

According to the letter, Apple cited “ongoing litigation” as the reason for its decision. The company is currently entangled in a highly public legal battle with Epic Games over its App Store policies. Klobuchar and Lee go on to point to the fact Apple has found ways to make witnesses available in similar situations in the past. They also reference testimony the company provided in the North Dakota Senate and Arizona House of Representatives when those two states considered their recent app store reform bills, and an interview Tim Cook did with The New York Times in which he talked about Epic and the App Store. If Apple ends up not taking part in the hearing, it will be particularly notable given that Google has agreed to comply with the panel.

“Apple’s sudden change in course to refuse to provide a witness to testify before the Subcommittee on app store competition issues in April, when the company is clearly willing to discuss them in other public forums, is unacceptable,” the letter concludes. We’ve reached out to Apple for comment, and we’ll update this article when we hear back from the company.

Update 4/11 4:25PM ET: Apple has sent a letter to Senators Klobuchar and Lee telling them that it will offer an executive after all, with Chief Compliance Officer Kyle Andeer now available to speak at the April 21 hearing.