U.S. Treasury Secretary Steven Mnuchin defied a congressional subpoena seeking six years of President Donald Trump’s tax returns on Friday, all but guaranteeing a federal court battle with Congress over the records.

In a widely expected move, Mnuchin rejected a demand for the documents from House Ways and Means Committee Chairman Richard Neal, saying the panel lacks “a legitimate legislative purpose” for obtaining the tax records that Democrats view as critical to their efforts to investigate Trump and his presidency.

“We are unable to provide the requested information in response to the committee’s subpoena,” Mnuchin said in a letter to Neal, released ahead of a 5 p.m. EDT deadline for delivering the documents.Neal later issued a statement, saying he was “consulting with counsel on how best to enforce the subpoenas moving forward.”

Hours earlier, the Democratic chairman had said he was inclined to turn to federal court to obtain Trump’s tax returns, if the administration missed the deadline. “We will likely proceed to court as quickly as next week,” Neal had told reporters.

Trump’s refusal to cooperate in numerous congressional probes of him, his family and his presidencying Democrats, who control the House of Representatives, to look to the courts to enforce their oversight powers under the U.S. Constitution.