Democratic Presidential candidate Joe Biden Joe BidenThe Memo: Warning signs flash for Trump on debates Senate Republicans signal openness to working with Biden National postal mail handlers union endorses Biden MORE ripped President Trump Donald John TrumpBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Military leaders asked about using heat ray on protesters outside White House: report Powell warns failure to reach COVID-19 deal could 'scar and damage' economy MORE's tweets on Iran as "dangerous and irresponsible" on Saturday night after Trump threatened to hit Iranian sites if there is retaliation for Qassem Soleimani's killing.

"When he makes statements like that, it just seems to me to be he's going off on a tweet storm on his own, and it's incredibly dangerous and irresponsible," Biden told reporters, according to a video posted to Twitter by CBS News's Bo Erickson.

"I have no idea whether he's coordinated with any of our allies. I have no idea whether or not he has the support of his own generals," the former vice president added. "This is a guy who seems to be unmoored."

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Earlier Saturday, Trump said he was prepared to strike 52 unspecified Iranian sites "very fast and very hard" if Iran retaliates for the death of Soleimani, who was one of Iran's top generals.

"Let this serve as a WARNING that if Iran strikes any Americans, or American assets, we have targeted 52 Iranian sites... some at a very high level & important to Iran & the Iranian culture, and those targets, and Iran itself, WILL BE HIT VERY FAST AND VERY HARD. The USA wants no more threats!" Trump tweeted.

The president this week directed a strike that killed Soleimani. He has defended the action, saying it was done to "stop a war."

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Democrats, however, have criticized the strike, calling it an escalation that could provoke violence.

Iran has threatened "harsh retaliation" for the strike.

Biden is among the frontrunners in the 2020 race for the Democratic presidential nomination.