Republican U.S. Senator Jeff Flake of Arizona criticized President Donald Trump over his trade policy on Thursday.

In his speech at the Senate floor, Sen. Flake warned his fellow lawmakers that the United States is in the early stages of a “full scale trade war.”

“I rise today to sound the alarm about the president's decision to impose steep tariffs on our trading partners. We are in the nascent stages of a full-scale trade war,” according to the senator.

Last week, the Trump administration announced tariffs on steel and aluminum imports from Canada, Mexico, and the European Union (EU). The tariff on imported steel and aluminum is 25% and 10%, respectively.

In his remarks, Sen. Flake emphasized that there is no guaranteed winner in a trade war. Instead, it guarantees that “there will only be losers.” He suggested that the Pres. Trump’s trade policy is “protectionism,” which “stifles innovation and reduces productivity.”

Additionally, he said, “These tariffs imposed on our allies will not and are not going unanswered.” He noted that some of them already “introduced retaliatory measures” against the United States.

Furthermore, Sen. Flake said he joined a bipartisan group of senators to introduce a legislation to rein in the President’s use of section 232 of the Trade Expansion Act of 1962 to justify protectionist measures. Republican Sen. Bob Corker of Tennessee is leading the effort.

Sen. Flake says Congress must show leadership

Moreover, the senator from Arizona pointed out that the Constitution granted Congress the authority to regulate tariffs and trade. It must  “show leadership” on the matter.

According to him, “We are elected to be leaders, not followers here. It is not our charge to just go along just because the President shares our party affiliation.

Separately, Sen. Flake reiterated to CNN’s Briana Kellar that the Constitution gave Congress not the President the primary role to regulate trade and tariffs. He said, “The President is using an exemption that was never intended for that purpose."

He also noted that it is not the first time, a number of Republican senators contradicted Pres. Trump.  Last week, Sen. Orrin Hatch of Utah said the tariffs on steel and aluminum are a tax hike on Americans.

Prior to his speech, the President slammed Sen. Flake. In a tweet, Pres. Trump said, "How could Jeff Flake, who is setting record low polling numbers in Arizona and was therefore humiliatingly forced out of his own Senate seat without even a fight (and who doesn't have a clue), think about running for office, even a lower one, again? Let's face it, he's a Flake!"