Key Republican Sen. Orrin Hatch threatened Tuesday to push for legislation to curb President Donald Trump's trade authority if he moves forward with more tariffs.

It marks the strongest warning yet issued by Hatch — a Trump supporter, chairman of the Senate Finance Committee and the longest serving Senate Republican — about pushing back against the president's tariff policy, which the senator has repeatedly criticized. If Hatch would back a bill to limit Trump's powers, he would become the most important Republican to do so.

"If the administration continues forward with its misguided and reckless reliance on tariffs, I will work to advance trade legislation to curtail presidential trade authority," the Utah Republican said on the Senate floor Tuesday. "I am discussing legislative options with colleagues both on and off the Finance Committee and I will continue to do so."

However, Hatch said that he would "much rather work with the administration to advance a trade agenda that serves the interests of the American people and job creators."

The senator's comments underscore the bubbling GOP opposition to Trump's tariff policy, which many Republican lawmakers have argued will damage both American consumers and businesses. As Trump recently put tariffs on most steel and aluminum imports and a variety of Chinese goods, prompting retaliation from major trading partners, some Republicans pushed for a measure to limit the president's authority.

Hatch's support would give such legislation powerful backing it so far lacks. He did not signal what specific action he would support.