Outspoken Trump critic Sen. Jeff Flake, R-Arizona, is lashing out against the administration's latest tariff policy leveled against U.S. allies, calling the move "not grown-up leadership" in excerpts of remarks he delivered on the Senate floor on Thursday. The administration announced the move to impose tariffs last week after President Trump initially proposed them back in March, deferring final action while trade negotiations proceeded.

Flake warns in excerpts that he tweeted Wednesday night that the U.S. is in the "nascent stages of a full-scale trade war" as the U.S.' closest trade partners have already vowed retaliatory measures to Mr. Trump's 25 percent tariff on imported steel and 10 percent on imported aluminum.

I plan to speak on the Senate floor tomorrow morning to discuss the administration’s protectionist policies and the importance of America's leadership in the world. Here is some of what I intend to say: pic.twitter.com/ox8HX75lsY — Jeff Flake (@JeffFlake) June 6, 2018

"What shall our friends make of such erratic behavior? How will they respond to such confusing actions? And, most importantly, how long will they remain our friends if this irrational approach continues?," Flake questions. "Muddled and mercurial, this is not grown-up leadership. Our allies are left baffled, confounded, often appalled" noting that valued international partnerships have been "shattered" by an "ill-considered tantrum."

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Flake fears that U.S. allies "will not wait for us to come to our senses. If we abandon our role as a leader in the world today, it may very well not be there tomorrow."

The senator compares the administration's hasty decision to that of the U.S. pulling out of the Trans-Pacific Partnership. "They did not give up on trade or come back to us on bended knee begging the United States to rejoin the process. They simply shrugged and continued on their own, leaving us behind."

After Mr. Trump's original tariff rollout, Flake announced that he would immediately draft legislation in an effort to block and nullify any of the president's tariff actions. "These so-called 'flexible tariffs' are a marriage of two lethal poisons to economic growth – protectionism and uncertainty," Flake said in a statement at the time.

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! — Donald J. Trump (@realDonaldTrump) June 7, 2018

Mr. Trump appeared to respond to Flake over twitter early Thursday morning, calling the senator "a flake."