FILE PHOTO: Chairman of the Senate Judiciary Committee Charles Grassley (R-IA) speaks during the second day of confirmation hearings on Senator Jeff Sessions (R-AL) nomination to be U.S. attorney general in Washington, U.S., January 11, 2017. REUTERS/Joshua Roberts/File Photo

WASHINGTON (Reuters) - U.S. Senate Finance Committee Chairman Charles Grassley said on Wednesday that Congress will not grant any expansion of President Donald Trump’s executive authority over tariff and other trade remedies.

“We ain’t going to give him any greater authority. We already gave him too much,” Grassley, an Iowa Republican, told reporters in response to a Bloomberg report that the White House is preparing a bill that would seek to give Trump broad authority to levy new tariffs to break down other countries’ non-tariff trade barriers.

Trump previously sought to expand his authority on trade with an attempt last year at legislation that would allow “reciprocal tariffs” and that would abandon key disciplines agreed at the World Trade Organization.

Trade has become one of the administration’s key priorities, with Trump seeking new trade pacts with China, Canada, Mexico, the European Union and Japan. Washington has already reworked the North American trade treaty with neighbors Mexico and Canada, though it has yet to be voted on by the new Congress.

Grassley said he thought concerns over labor and other elements of the agreement held by Democratic lawmakers could be addressed through side letters, rather than renegotiation of the deal.

Steel and aluminum tariffs on Canada and Mexico are hurting farmers and “those have to go” in order to get agricultural interests to support congressional approval the new U.S.-Mexico-Canada Agreement trade deal, Grassley said.