Supreme Court Chief Justice John Roberts is set to rule within the next few days as to whether Special Counsel Robert Mueller can subpoena an unknown government-owned foreign corporation.

Anticipation is growing in Washington, D.C. as the nation is set to learn the identity of the state-owned entity that has tried to block Mueller from revealing its alleged role in the Russia investigation.

Roberts surprised legal analysts last Sunday when he temporarily blocked the subpoena and forced Mueller to explain why the government was investigating a foreign-backed corporate entity whose government has been trying hard to avoid cooperating.

Mueller’s prosecutors filed a brief on Friday night, according to Politico.

Roberts will review Mueller’s submission and then decide whether to uphold the ruling of the lower court - the D.C. Circuit Court of Appeals - which said earlier this month that the corporation was required to abide by the subpoena.

Supreme Court Chief Justice John Roberts is set to rule within the next few days as to whether Special Counsel Robert Mueller can subpoena a government-owned foreign corporation

Roberts could decide to deny the company’s appeal, or he could rule that the case needs to be heard by all nine Supreme Court justices.

The case is unusual since the unnamed country involved has gone to great lengths to fight Mueller’s subpoena - leading to speculation that it has something to hide in the ongoing Russia investigation.

In its arguments before the D.C. Circuit Court, the company claimed that complying with the subpoena meant violating the laws of its home country.

But the judges unanimously rejected this argument.

Last Sunday, Roberts shocked legal observers when he agreed to take up the company’s emergency petition and stay the lower court’s ruling.

The mystery remains as to what Roberts saw in the filing documents that made him cast doubt on the ruling of the D.C. Circuit Court.

This is the first known legal challenge in the Mueller investigation to make its way to the Supreme Court.

The range of possibilities on the company's identity is vast, CNN reports. It could be anything from a sovereign-owned bank to a state-backed technology or information company.

These types of companies have been frequent recipients of requests for information in Mueller's investigation.

The company had been required to turn over 'information' about its commercial activity in the criminal investigation, CNN reported.

The appeals court also said the company could face fines for every day of noncompliance. Roberts' holding order also puts a pause on any fines it would wrack up.

There has been an usual level of secrecy surrounding the unidentified company and the case.

When it was argued at the D.C. circuit court earlier this month, the courtroom was closed to the public, Politico reported.

Court personnel ordered journalists to leave the floor where lawyers were presenting their positions.

Mueller and multiple congressional committees are looking into allegations that there was collusion between Russian operatives and Trump associates during the presidential campaign and transition.

The case is unusual since the unnamed country involved has gone to great lengths to fight Mueller’s subpoena - leading to speculation that it has something to hide in the ongoing Russia investigation

In January 13, 2017, the Senate select committee announced that it was conducting a probe of Russian meddling in the 2016 Presidential Election.

The investigation was sparked by a declassified report from the Director of National Intelligence (DNI) that described a multifaceted effort led by Russian President Vladimir Putin to interfere with the election by releasing damaging information about Hillary Clinton to help Donald Trump.

It is understood that the company's challenge of the subpoena appears to have begun in September.

In its ruling this past week, the U.S. Circuit Court of Appeals for the District of Columbia gave few clues about the company and its country of origin or what Mueller's team sought.

In a three-page decision obtained by CNN, the Supreme Court judges describe how they had learned confidentially from prosecutors that they had 'reasonable probability' the records requested involved actions that took place outside of the United States but affected the U.S.

Prosecutors claim that the Mueller team is also examining actions related to Turkish, Ukrainian and other foreign government interests.

Mueller has already indicted three Russian companies and 25 Russians for their alleged contributions to a social media propaganda scheme meant to influence American voters and to the hack of the Democratic Party.

The special counsel and other Justice Department units continue to pursue several investigations related to Mueller's investigation.

Mueller and multiple congressional committees are looking into allegations that there was collusion between Russian operatives and associates of President Donald Trump (above) during the presidential campaign and transition

It is thought that Mueller is nearing the end of his investigation and could submit his confidential report to the attorney general as early as February.

Mueller is now tying up loose ends in his investigation into allegations of 'links and/or coordination' between the Trump campaign and the Russian government, U.S. officials and others familiar with the situation told NBC News.

Nineteen months into his investigation, Mueller has yet to publicly provide evidence of the central crime he was appointed to investigate: a conspiracy between members of Donald Trump's campaign and the Russian government to influence the 2016 election.

Mueller is also known to be investigating Trump for possible obstruction of justice, including over the firing of FBI Director James Comey.

When it is complete, Mueller's report will likely go to Bill Barr, Trump's appointee as attorney general who has yet to be confirmed.