Treasury Secretary Steven Mnuchin said Wednesday that it's up to the courts to referee his dispute with House Democrats demanding access to President Donald Trump's tax returns.

Mnuchin told a Senate panel that the fight between the administration and the House Ways and Means Committee chairman, Rep. Richard Neal, "will go to the third branch of government to be resolved."

Neal, D-Mass., has subpoenaed six years' worth of Trump's returns with an eye to examining whether Trump is paying all the taxes he owes and whether his web of businesses has created conflicts of interest with his official actions as president. Neal has set a Friday deadline for the IRS to deliver them.

But Mnuchin said that the Treasury Department was unlikely to comply.

"We haven't made a decision but I think you can guess which way we're leaning on our subpoena," Mnuchin said, adding, "I take great comfort that there is a third branch of government to deal with this important issue."

Mnuchin is sticking to earlier arguments that Neal's demand for Trump's taxes would set a precedent that lawmakers could pursue confidential tax information for political purposes. He said Treasury and IRS lawyers agree with his interpretation that a 1924 law that requires him to "furnish" the returns to Neal does not apply in this case because there is no legitimate legislative purpose to Neal's request.

Mnuchin said the tax tussle was "a very important issue that has a precedent way beyond any one president and Congress."

"There is a difference in interpretation between Congress and us and the Department of Justice around this law that not only impacts this president and this Congress but has a very big impact on every single taxpayer in weaponizing the IRS," Mnuchin said. "And this is why there are three branches of government."