WASHINGTON, Jan 16 (Reuters) - The Trump administration violated federal law last year by withholding security aid for Ukraine that had been appropriated by Congress, a U.S. congressional watchdog said in a report released on Thursday.

"Faithful execution of the law does not permit the President to substitute his own policy priorities for those that Congress has enacted into law. OMB withheld funds for a policy reason, which is not permitted under the Impoundment Control Act (ICA)," the U.S. Government Accountability Office said, referring to the Office of Management and Budget. "The withholding was not a programmatic delay. Therefore, we conclude that OMB violated the ICA." (Reporting by Tim Ahmann and Susan Heavey Editing by Chizu Nomiyama)

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