U.S. Senator Bernie Sanders has warned that a military confrontation between the U.S. and Iran would be more disastrous than the Iraq war.

“Right now if you can believe it, Trump and his people in his administration apparently have learned nothing from that horrific war in Iraq. And you have (national security adviser) John Bolton and others talking about the need to go to war in Iran,” Fox News quoted him as saying on Monday.

Sanders, who is making his second straight bid for the Democratic presidential nomination, said, “If you think the war in Iraq was a disaster, my strong belief is a war with Iran would be much worse…Not only would a war with Iran be a disaster, it happens to be unconstitutional.”

He told MSNBC on May 14, “It is almost impossible to imagine that after the horror of the war in Iraq when we were lied to by the Bush administration and one of the leading architects was this very same, John Bolton.”

Sanders also tweeted that “If we go to war with Iran, we will destabilize the entire region and thousands of Americans and Iranians will die.”

“I am working right now with my Republican colleagues to stop this disastrous rush to war,” he added.

More than 70 retired American military leaders wrote an open letter to U.S. President Donald Trump urging him to avoid war with Iran.

The former generals advised Trump in the letter published Thursday in War on the Rocks to take “crisis de-escalation measures.”

“As President and Commander-in-Chief, you have considerable power at your disposal to immediately reduce the dangerous levels of regional tension,” the letter read. 

“Crisis de-escalation measures should be established with the Iranian leadership at the senior levels of government as a prelude to exploratory diplomacy on matters of mutual concern.”

Trump said Friday that he would send about 1,500 troops to the Middle East.

Tension has been rising between Iran and the U.S. since the Trump administration ended sanctions waivers for the remaining importers of the Iranian oil and the Pentagon sent the USS Abraham Lincoln carrier strike group and a bomber task force to the Persian Gulf and made military threats against Iran. 

The USS Arlington transports marines, amphibious vehicles, and rotary aircraft, as well as the Patriot missiles, are planned to join the carrier strike group.

Oman’s Foreign Ministry tweeted on Friday that Muscat is trying “with other parties” to reduce tensions between the U.S. and Iran.

“There is a danger that a war breaks out, hurting the whole world ... Both parties, the American and the Iranian, are aware of the danger,” the tweet cited Omani Foreign Minister Yousuf bin Alawi bin Abdullah as saying in an interview with an Arabic publication, according to Reuters.

NA/PA