President-elect Donald Trump could soon face resistance within his own party over his tariff threats.

A staffer for Republican Senator Mike Lee told trade experts at a lunch in Washington this week that he is looking into ways to curtail the president's wide-ranging powers to impose tariffs, according to one of Lee's aides.

The aide said a bill could be introduced as early as next week, and it may require Trump to go through Congress to use tariffs.

Lee, who represents Utah, declined to comment for this story. Trump's spokesperson did not respond to a request for comment.

The aide emphasized that the bill is not just a push against Trump on trade, but part of a broader effort to transfer more legislative power to Congress from the executive branch.

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Trade experts who attended the lunch said no major specifics were discussed. Even if it is not passed, this effort to reel in Trump's trade powers could change the optimistic narrative on tariffs that Trump has cast.

"It's a useful shot across the bow, it's going to tell the president that this is going to be more difficult than he might think," says William Reinsch, a trade expert at the Stimson Center, a non-partisan research group in Washington. Reinsch attended the lunch.

Trump often uses the threat of tariffs to try to keep jobs in America or get better trade deals. Experts warn that tariffs could actually cost U.S. jobs and make prices go up for Americans -- as they have in the past.

Lee's bill could also be a wake up call for Congress: Under current laws, Trump doesn't need to consult with Congress before slapping tariffs on countries.

"A president who wants to restrict trade enjoys almost carte blanche authority," Gary Clyde Hufbauer, a trade expert and senior fellow at the Peterson Institute of International Economics, wrote in a recent blog post.

Related: World Bank cuts forecast, cites protectionism

In a September report, Hufbauer outlined several ways a president can use tariffs without input from Congress. In some instances, he said the president can declare a "national emergency" -- which has a broad definition -- and then slap big tariffs on China, Mexico or anyone else.

In the Constitution, Congress has the right to impose tariffs on other nations.

But since the 1930s when Congress started a bruising trade war, lawmakers have slowly transferred trade powers to the president. Now Lee may be trying to claw those back.

Historically, the president has pushed for more free trade policies while Congress has advocated for more protectionism. The tables have turned under Trump.

"This is a very different dynamic," says Edward Alden, a senior fellow at the Council on Foreign Relations, who also attended the lunch with Lee's staffer. "The tendency has been for Congress to push the administration to be more restrictive."

As for Lee's potential bill, details remain unclear about how exactly trade powers would transfer from the president to Congress. It's also not known if there are any co-sponsors on the bill.

Lee's push to curtail Trump's powers echoes the sentiment of House Speaker Paul Ryan.

"We're not going to be raising tariffs," Ryan told radio host Hugh Hewitt on January 4.