Senate Finance Committee Chairman Chuck Grassley Charles (Chuck) Ernest GrassleyThe Hill's 12:30 Report: Ginsburg lies in repose Top GOP senators say Hunter Biden's work 'cast a shadow' over Obama Ukraine policy Read: Senate GOP's controversial Biden report MORE (R-Iowa) condemned President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE's new tariffs on Mexico late Thursday, calling the move a "misuse" of presidential tariff authority and cautioning the levies could derail passage of the United States-Mexico-Canada Agreement (USMCA).

"Trade policy and border security are separate issues. This is a misuse of presidential tariff authority and counter to congressional intent," Grassley said in a statement.

The lawmaker cautioned that following through on Trump's tariff threat "would seriously jeopardize passage of USMCA," a revision of the North American Free Trade Agreement (NAFTA).

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"I support nearly every one of President Trump’s immigration policies, but this is not one of them," he added.

Trump announced he would impose the tariffs to pressure Mexico to stop the flow of migrants into the U.S. via the southern border.

"On June 10th, the United States will impose a 5% Tariff on all goods coming into our Country from Mexico, until such time as illegal migrants coming through Mexico, and into our Country, STOP. The Tariff will gradually increase until the Illegal Immigration problem is remedied," he tweeted late Thursday.

The tariff will increase by 5 percent each month until it reaches 25 percent “unless and until Mexico substantially stops the illegal inflow of aliens coming through its territory,” the president said a statement distributed by the White House.

The move could rattle financial markets at a precarious time for the president’s trade policy, as the White House pressures Congress to approve Trump’s revision of NAFTA.

Dow futures plummeted more than 200 points on Thursday evening after the president announced the new tariffs.

Grassley had previously threatened to derail Trump's central trade achievement over continued steel and aluminum tariffs. Last week, Trump hinted that he had reached a deal to drop those tariffs, paving the way for the USMCA in the Senate.

Even with Grassley's approval, Trump will face a hurdle passing the agreement in the House, where Speaker Nancy Pelosi Nancy PelosiHoyer: House should vote on COVID-19 aid — with or without a bipartisan deal Ruth Bader Ginsburg lies in repose at Supreme Court McCarthy threatens motion to oust Pelosi if she moves forward with impeachment MORE (D-Calif.) has insisted on labor and enforcement improvements to the deal.

Earlier Thursday, Trump formally kicked off the approval process for the deal, setting off a timeline for its passage in Congress.

Pelosi derided the decision, meant to pressure Congress to pass the deal, saying it “indicates a lack of knowledge on the part of the administration on the policy and process to pass a trade agreement.”