Democratic presidential candidate and former U.S. Vice President Joe Biden speaks during a forum held by gun safety organizations the Giffords group and March For Our Lives in Las Vegas, Nevada, October 2, 2019.

Joe Biden warned Tuesday that President Donald Trump is charging toward a crisis in Iran, as the Democratic presidential candidate cast himself as a steady hand best equipped to manage spiking tensions in the Middle East.

The former vice president has long described Trump as a reckless leader ill-equipped for foreign policy challenges. Biden has stepped up criticism of the president's decision-making since the U.S. on Thursday killed Iran's top general, Qasem Soleimani — an action he and his Democratic rivals warn could lead to another war in the region.

"A president who says he wants to end endless wars in the Middle East is bringing us dangerously close to starting a brand new one," Biden said during remarks in New York. He pointed to Trump sending thousands more troops to the Middle East despite saying he wants to leave the region.

Biden pointed to his own experience — eight years as vice president and more than three decades in the Senate — to argue for his ability to navigate the crisis. He said Trump opened the door to conflict by pulling out of the Iran nuclear deal — an international agreement meant to stop Tehran's development of weapons reached during the Obama administration.

Iran has stopped complying with major parts of the deal.

Biden said he has "no illusions" about Iran, which he said has "sponsored terrorism and threatened our interests." But he argued "there's a smart way" to counter Tehran, rather than a "self-defeating way."

The former vice president argued Trump should both rejoin the nuclear agreement and explain the "imminent threat" the administration cited in killing Soleimani. He also contended Trump does not have the authority to carry out war with Iran without congressional approval.

The Trump campaign did not immediately respond to CNBC's request to comment on Biden's criticism.

The top contenders for the 2020 Democratic presidential nomination have used the deepening crisis in Iran to illustrate their foreign policy credentials. Biden's efforts to do so have opened him up to criticism.

The former vice president voted to authorize military force against Iraq in 2002 — though he went on to harshly criticize the prolonged and destructive war. Biden has suggested on the campaign trail that he opposed the war from the beginning, which his campaign has called a misstatement.

Sen. Bernie Sanders, one of the top contenders to face Trump next year, has criticized Biden over Iraq in recent days.

"Joe Biden voted and helped lead the effort for the war in Iraq, the most dangerous foreign policy blunder in the modern history of this country," he told CNN on Monday in arguing Biden does not have the record to beat Trump.

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