The federal government filed a sealed response Friday to an unnamed foreign company’s fight to get the Supreme Court to weigh in on a mysterious grand jury subpoena rumored to be connected to Special Counsel Robert Mueller’s Russia probe.

The filing’s contents are hidden from public view and it does not mention Mueller’s office, but was filed before a Dec. 31 deadline set by Supreme Court Chief Justice John Roberts.

Details of the clash between the company and prosecutors remained unclear, but Politico reported it may involve Mueller’s team due to its secrecy.

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A federal court last week ruled against the company’s effort to quash the subpoena. The D.C. Circuit Court of Appeals held the company in contempt and rejected its arguments that its governmental ownership makes it immune from a grand jury subpoena.

The court also rejected that company’s request that it should be excused from responding to the subpoena because it violated the Foreign Sovereign Immunities Act and that the subpoena was unenforceable, the Hill reported.

Mueller’s team has not publicly commented on the dispute, while lawyers for President Trump said the case does not involve the president.

“We’re not involved in it — we’re not aware of the nature or scope of the litigation,” Jay Sekulow, one of the president’s lawyers, told the New York Times.

Aside from Mueller's probe into possible ties between the Trump campaign and Russia during the 2016 election, the special counsel has reportedly investigated actions involving other countries as well, including Turkey, Ukraine and the United Arab Emirates, according to the Hill.

If the Supreme Court decides not to deal with the case, details of the fight and the identity of the company could remain secret, according to Politico.

Fox News reporter Andrew O'Reilly contributed to this report.