President Donald Trump lost a key round Friday in the legal fight over whether members of Congress can get access to his personal and corporate tax returns.

In a 2-1 ruling, judges on the U.S. Court of Appeals for the District of Columbia Circuit said House Democrats can enforce a subpoena for the documents.

The ruling upholds a lower court's decision, leaving the president's attorneys with few ways to block his accountants, Mazars LLP, from complying with the House Oversight Committee's demands.

Trump could ask for a new decision from the full D.C. Circuit appeals court. That typical next step would leave him with only the U.S. Supreme Court as a last resort if he loses again.

An administration official with knowledge of the case said Friday that Trump will 'in all likelihood be headed to the Supreme Court for [legal] relief.'

President Donald Trump has lost the most recent round in his legal fight to keep his personal and corporate income tax returns out of the hands of his enemies in Democrat-controlled congressional committees that are investigating him

The House Oversight and Reform Committee, led by Maryland Democratic Rep. Elijah Cummings, subpoenaed Trump's accountants at Mazars LLP for his tax records

The high court could refuse to hear the case. It could also grant a hearing and press pause on the subpoena while the dispute winds its way toward a final resolution in 2020 – while Trump is in the thick of a re-election fight.

His attorneys Trump had argued that U.S. District Judge Amit Mehta should have reversed the subpoena.

And the president had sued the House committee in April, arguing unsuccessfully that investigating his personal finances from years predating his time in office goes beyond the constitutional powers of Congress.

Democrats are looking for evidence of conflicts of interest and payments from foreign governments that could justify impeaching President Trump.

'Disputes between Congress and the president are a recurring plot in our national story,' Judge David Tatel wrote in the 66-page opinion. 'And that is precisely what the Framers intended.'

Trump's lawyers have insisted that Congress can only see his financial records from years before he was president if it is engaged in a formal impeachment process; House Speaker Nancy Pelosi has not taken a vote to authorize one

'The fact that the subpoena in this case seeks information that concerns the President of the United States adds a twist, but not a surprising one,' he added.

Tatel was appointed by President Bill Clinton. Judge Patricia Millett, an Obama appointee, sided with him.

The lone dissent in Friday's ruling came from Judge Neomi Rao, who Trump nominated to the bench this year.

Eleven judges sit on the full D.C. Circuit appeals court. Six of them were appointed by Democratic presidents.

Rao wrote on Friday that Congress can only get Trump's tax records if it is officially engaged in an impeachment proceeding, something House Speaker Nancy Pelosi has not taken a vote to authorize.

'Upholding the subpoenas 'would turn Congress into a roving inquisition over a co-equal branch of government,' she added.

A knowledgeable administration official said Friday that Trump will 'in all likelihood be headed to the Supreme Court' as Democrats try to enforce their subpoena

Trump broke a tradition, but not a law, in keeping his tax returns private; but his accountants don't have the ability to resist a congressional subpoena without intervention from the courts

'The most important question is not whether Congress has put forth some legitimate legislative purpose, but rather whether Congress is investigating suspicions of criminality or allegations that the President violated a law,' Rao wrote, declaring that the House of Representatives 'may not use the legislative power to circumvent the protections and accountability that accompany the impeachment power.'

Oversight committee Chairman Elijah Cummings said in a statement that the ruling 'is a fundamental and resounding victory for Congressional oversight, our Constitutional system of checks and balances, and the rule of law. For far too long, the President has placed his personal interests over the interests of the American people.'

The three-judge panel said Mazars doesn't have to comply with the House subpoena right away, granting a 7-day reprieve while Trump's lawyers file their next inevitable appeal.

Trump broke a relatively recent tradition by not publishing his income tax returns as he ran for president as a major party nominee.

No law requires him to release the documents. By entrusting them to bankers and accountants, however, he provided Democrats in the Legislative Branch of the federal government with a way around his privacy concerns.

It remains up to the Judicial Branch to decide whether taking that route violates Trump's constitutional rights as the leader of the Executive Branch.