Democratic presidential candidates are urging caution when it comes to Iran, after Iran shot down a U.S. drone in what the U.S. says is international airspace. Late Thursday night, the president ordered a strike on Iran, but backed off, he said, after learning the likely human toll

 

Democratic presidential candidates are urging Mr. Trump, who campaigned on getting the U.S. out of wars in the Middle East, to turn to diplomacy rather than aggressive military action. Mr. Trump said the strike he was "cocked and loaded" for -- which he said could have killed 150 people -- was not "proportional" to the drone strike carried out by Iran.

"Donald Trump promised to bring our troops home. Instead he has pulled out of a deal that was working and instigated another unnecessary conflict. There is no justification for further escalating this crisis—we need to step back from the brink of war," Sen. Elizabeth Warren tweeted late Thursday night, upon news that Mr. Trump had ordered the strike but pulled back. 

Former Vice President Joe Biden, who led the Senate Foreign Relations Committee when he was in the Senate and took over many of the Obama administration's foreign policy initiatives, called Mr. Trump's Iran strategy a "self-inflicted disaster."  

"Two of America's vital interests in the Middle East are preventing Iran from obtaining a nuclear weapon and securing a stable energy supply through the Strait of Hormuz. Trump is failing on both counts," Biden said in a series of tweets Thursday. "He unilaterally withdrew from the hard-won nuclear agreement that the Obama-Biden Administration negotiated to stop Iran from getting a nuclear weapon. Trump promised that abandoning the deal and imposing sanctions would stop Iran's aggression in the region. But they've only gotten more aggressive. Trump also promised that walking away would somehow lead to a better deal – instead, the predictable has happened: Iran is building back up its nuclear capability."

Sen. Bernie Sanders said war with Iran would mean "endless conflict." 

"Congress must assert its constitutional authority and stop Trump from going to war," Sanders tweeted Friday morning

Sen. Cory Booker also expressed concern about Mr. Trump overstepping his authority in authorizing a strike without Congress' approval.

"To be absolutely clear, the 2001 AUMF does not grant the president authority to strike Iran — for that, he must go to Congress. Any military action in Iran that circumvents congressional approval is a blatant and unconstitutional power grab," Booker said in a statement. 

It's unclear what Mr. Trump will do next, after calling off the strike. The president said further sanctions have been imposed on Iran, but the Treasury Department hasn't made any announcements. 

Many of the Democratic presidential candidates are in South Carolina Friday, some of them gathered in the same place for the first time. They will likely have more opportunities to address mounting tensions with Iran then.