FILE PHOTO: A general view of the U.S. Internal Revenue Service (IRS) building, with the partial quote "taxes are what we pay," in Washington May 27, 2015. REUTERS/Jonathan Ernst

WASHINGTON (Reuters) - A deadline for the U.S. Internal Revenue Service to turn President Donald Trump’s tax returns over to a congressional tax oversight committee expired on Tuesday without lawmakers receiving the documents, a committee aide said.

The outcome, which was widely expected, could prompt Democrats who control the tax-writing House Ways and Means Committee to subpoena the documents, as an opening salvo in what many expect to be a lengthy court battle that might have to be settled by the U.S. Supreme Court.