WASHINGTON (AP) — President Donald Trump faced pushback Monday from Republican lawmakers, an influential GOP group and foreign leaders over his tough negotiations that are hitting China, Canada and Mexico with tariffs amid fears of a trade war.

But the president defended his actions saying the U.S. would soon be in a stronger position with its top trading partners.

Trump wrote in a series of tweets that his trade negotiations with China and a slew of U.S. allies would break down large trade barriers faced by American farmers. He said that China "already charges a tax of 16% on soybeans. Canada has all sorts of trade barriers on our Agricultural products. Not acceptable!"

In a conference call later Monday with grassroots supporters, he said: "We will be in a very strong position very soon. We don't want to be taken advantage of anymore."

The president last week imposed tariffs on steel and aluminum imports from top U.S. trading partners, including Canada, Mexico and the European Union. And he has threatened tariffs on up to $200 billion in Chinese imports, raising the potential for retaliation in a dispute involving the globe's two largest economies.

Senate Republicans have warned that the tariffs could dampen the economic gains from the GOP tax cuts and sour the mood among voters as lawmakers campaign to protect the Republican majority in Congress in November midterm elections.

Sen. Bob Corker, R-Tenn., said he met with senators Monday as they consider a legislative response, drawing interest from "both sides of the aisle" who are concerned about the tariffs.

The lawmakers were trying to draft a narrowly focused bill that would require a vote in Congress to approve tariffs when the administration claims they're needed for national security, as it did for those on steel and aluminum from the top U.S. allies.

It's a longshot legislative strategy, but the group was working quickly to try to produce an amendment that could win support in time for debate on a separate, must-pass defense bill.

White House legislative affairs director Marc Short dismissed the chatter. "To suggest that it's news that Congress would want to reclaim powers that belong to the executive branch, I don't think is exactly newsworthy," he said on CNN.

Many Farm Belt lawmakers worry that the trade disputes could make American farmers the target of retaliation. Mexico, for example, has said it will penalize U.S. imports including pork, apples, grapes and cheeses.