Senate Foreign Relations Chairman Bob Corker plans to make a pitch to Republican colleagues at the Senate lunches Tuesday on a proposal to require a congressional vote on future tariffs involving national security before they can take effect.

The Tennessee senator said he’s found Democrats who are interested in the proposal, but he would not identify them. The fiscal 2019 defense authorization bill is a likely vehicle for the proposal, he said, “because it deals with national security. That would be the best vehicle.”

The Senate defense authorization bill includes provisions to address concerns about Chinese firms, acting on behalf of Beijing, buying or investing in U.S. businesses developing important technology. The legislation from Majority Whip John Cornyn would expand security reviews by the Committee on Foreign Investment in the United States to include deals that involve foreign control of U.S. real estate assets and concessions near military bases, airports and seaports and would limit the president’s power to lift sanctions on two Chinese companies.

Corker said he’d know later this week if he has sufficient support for the idea from Republicans and Democrats.

“Around here, getting anything added to a piece of legislation is like moving boulders,” he told reporters Tuesday night. “We’ll see. I’m going to try to sell it tomorrow.”

Corker said he has met with colleagues about his proposal but offered no specifics. “I think there is definite interest. I know there is interest on both sides of the aisle,” he said.

Lawmakers have expressed frustration with President Donald Trump’s trade actions, particularly the imposition of steel and aluminum tariffs on close allies such as Canada, Mexico and the European Union under Section 232 of the Trade Expansion Act of 1962. He slapped 25 percent tariffs on steel imports and 10 percent on aluminum imports after the Commerce Department concluded that foreign-made steel and aluminum are economic and national security threats and that imports have forced domestic plants to close and made the United States increasingly dependent on steel and aluminum imports for commercial and military uses.

Corker said he has spoken with Senate Majority Leader Mitch McConnell, but said the Kentucky Republican wants to take all possibilities under consideration.

Senate Agriculture Chairman Pat Roberts said he “would have to take a hard look at Mr. Corker’s language and give it very thoughtful study.” The Kansas Republican has expressed fears that threatened countermeasures by other countries could hurt U.S. businesses, particularly the agriculture sector, which is dependent on exports.

Corker’s move to push back against Trump’s trade actions comes as a network of political organizations associated with the billionaire brothers Charles and David Koch announced that it would fund an aggressive campaign on the benefits of free trade and against Trump’s protectionist views.