WASHINGTON -- The Trump administration says it's considering "consequences" for NATO ally Turkey if Turkey doesn't throw out the charges or acquit an American pastor accused of espionage and aiding terrorist groups.

The top U.S. diplomat for Europe, Wess Mitchell, tells a House committee that the pastor, Andrew Brunson, is "clearly innocent" of the charges. Mitchell says the State Department is consulting with Congress about "possible measures" against Turkey if Brunson isn't freed.

Mitchell's comments come a day after President Donald Trump tweeted in defence of Brunson. Trump called Brunson "a fine gentleman and Christian leader in the United States," who is "being persecuted in Turkey for no reason."

The 50-year-old evangelical pastor from North Carolina faces up to 35 years in prison. Brunson denies any wrongdoing.