Anti-war demonstrations erupted across major U.S. cities on Sunday, while prominent politicians in the country openly criticized the U.S.-Israel joint military actions against Iran. 

According to U.S. media reports, masses have rallied and marched to demonstrate their disapproval of the joint military operation in cities including Washington, Chicago, Boston, New York and Los Angeles. 

Top politicians in the country also criticized this military operation and its lack of congressional oversight.

Kamala Harris, a former vice president of the United States, on Saturday accused U.S. President Donald Trump of "dragging the United States into a war the American people don't want."

"Let me be clear," Harris wrote on social media. "I am opposed to a regime-change war in Iran, and our troops are being put in harm's way for the sake of Trump's war of choice."

In a statement released by U.S. Senate Democratic Leader Chuck Schumer following the strike, he said, "The administration has not provided Congress and the American people with critical details about the scope and immediacy of the threat."

As Schumer urged the administration to brief Congress, he also criticized that "President Trump's fitful cycles of lashing out and risking wider conflict are not a viable strategy" when it comes to handling conflicts with Iran.

U.S. Democratic Senator Tim Kaine on Saturday strongly criticized the U.S. military strike on Iran in a statement, calling it a "dangerous, unnecessary, and idiotic action."

"For months, I have raised hell about the fact that the American people want lower prices, not more war – especially wars that aren't authorized by Congress, as required by the Constitution, and don't have a clear objective," Kaine said. These strikes are a "colossal mistake," he said.

Tammy Duckworth, a U.S. senator and Illinois Democrat, said, "President Trump is not living up to the promises he made to Americans. We were not under imminent attack when he launched his attack on Iran. He did not consult with Congress. And, he certainly did not adhere to his promises to American people of getting us out of forever wars."

The United States and Israel on Saturday initiated "major combat operations" against Iran, plunging the conflict-ridden Middle East into yet another violent confrontation.