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WASHINGTON — President Donald Trump's lawyers cannot try to derail a lawsuit over his ownership of the Trump Hotel in Washington by appealing a key early ruling in the case, a federal judge said Friday, dealing another blow to the president's efforts to block the case from going forward.

The attorneys general of Maryland and Washington, D.C., claim that Trump is violating the Constitution's emolument's clauses, which bar the president from receiving "any present, emolument, office or title of any kind whatever from any king, prince, or foreign state" or any state in the U.S. The lawsuit claims that he improperly benefits financially when foreign or state governments patronize the hotel he owns just a few blocks from the White House.

The Trump legal team sought authority from the federal judge in the case, Peter Messitte of Maryland, to appeal the judge's pre-trial decision that the emoluments clauses are intended to protect against any type of potentially improper influence.

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Justice Department lawyers argued that the term "emolument" has a very specific meaning — a payment made to a public official in addition to the official salary. Under that reading, financial benefits from an office holder's private business dealings would be exempt.

In his order Friday, Messitte said the government cannot appeal the case piecemeal and must wait for a final ruling after a trial. He also declined to put a hold on the case, which would have blocked the challengers from seeking evidence about his hotel business through the legal process known as discovery.

He ordered lawyers for Maryland and Washington, D.C., to submit a schedule for discovery within 20 days. That order can be appealed.

"This is another major win for us in this historic case," said Karl Racine, Washington's attorney general. "We will soon provide the court a new schedule to begin the process of getting information about how President Trump is profiting from the presidency."

The Justice Department, which is representing Trump, had no comment on Friday's ruling.

Brian Frosh, the attorney general of Maryland, told NBC News that he hopes to begin the discovery process soon, but expects it to be three to four months until they get documents. He added that his office might need to depose Trump employees and potentially Trump himself.

He added that his wishlist of documents includes "financial records of the hotel, who stays there, what they paid."

"We know foreign governments stay there as well as state governments," he said. "It's not a very high bar to prove the president has taken emoluments in violation of the constitution."

"No other president has stepped anywhere near the line and Trump has blown across it," he said. "He should only get his salary and nothing else."