Rep. Ilhan Omar, D-Minn, one of Congress' most vocal critics of President Trump, placed the blame squarely on the White House after Iran announced it could enrich uranium up to 20 percent -- just a step below weapons-grade level.

The tension between the U.S. and Iran has been increasing in recent days after a high-profile attack on two oil tankers in the Strait of Hormuz. The U.S. blamed Iran for the attacks, which the country denied.

Iran said it would break a limit on uranium stockpiles established by the 2015 agreement with world powers that was intended to restrict the Islamic Republic's nuclear program in exchange for an easing of international sanctions.

Omar said, "none of this would be happening if Trump didn't back out of the Iran nuclear deal." She said the U.S. should get back to negotiations with Tehran and reinstate the Iran nuclear deal.

Trump declared Iran was responsible for the attacks in the Gulf of Oman, pointing to video released by the U.S. Navy that they claimed showed an Iranian vessel removing an unexploded mine.

"Iran did do it and you know they did it because you saw the boat,” Trump said during an interview on "Fox & Friends" last Friday. "They're a nation of terror and they've changed a lot since I've been president, I can tell you."

Omar took to Twitter on Monday condemning Trump's decision to pull out of the Iran nuclear deal shortly before the Pentagon approved sending 1,000 more troops to the Middle East in response to the attack.

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Critics slammed Omar for "appeasing the world's largest state sponsor of terrorism."

Iran's announcement raised pressure on Europeans trying to save the accord a year after the U.S. withdrawal.

President Hassan Rouhani already has warned Europe that a new deal needs to be in place by July 7 or the Islamic Republic would increase its enrichment of uranium.

Rouhani, greeting France’s new ambassador to Tehran on Monday, similarly warned that time was running out on the deal.

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“The current situation is very critical and France and the other parties to the (deal) still have a very limited opportunity to play their historic role for saving the deal,” Rouhani said, according to his website.

Fox News' Edmund DeMarche and The Associated Press contributed to this report