While peace advocates and his more progressive 2020 rivals remain outspoken in their demand for deescalation and telling President Donald Trump to end his reckless march to war, former Vice President Joe Biden is being chided for issuing a weak-tea response after Iranian missiles hit U.S. military bases in Iraq Tuesday night—a direct retaliatory strike following last week's U.S. assassination of top military leader Qasem Soleimani.

"The American people do not want war with Iran... Congress cannot stand by. It must act now to pass our legislation to uphold the Constitution and prevent Trump from spending trillions more on endless war." —Sen. Bernie Sanders"I'm going to hold off on commenting on the news tonight until we know more," Biden tweeted shortly after the Iranian attack was reported, "but there is one thing I will say: Jill and I are keeping our troops and Americans overseas in our prayers. We hope you'll keep them in yours."

Compared to Sens. Bernie Sanders and Elizabeth Warren, who have both spoken out repeatedly and forcefully in recent days against Trump's aggression and the threat of war, Biden's remarks were taken as a troubling signal that he has yet to learn key lessons since he voted in favor of the 2003 invasion of Iraq while serving in the U.S. Senate.

If your candidate right now is saying anything other than "the US cannot go to war with Iran and should de-escalate immediately," they shouldn't be your candidate https://t.co/ds4RqGbBSI — Kate Aronoff (@KateAronoff) January 8, 2020

"May I suggest 'No war with Iran'," said progressive radio show host Sam Seder in response to Biden's tweet.

At a campaign rally in New York, Biden's advice to Trump was not to immediately halt hostilities but rather to express hope that the president is "listening to his military commanders for the first time because so far that's not been the case."

It is this Democratic timidness that lead people like Joe Biden to vote for the war in Iraq. https://t.co/kTpXrVDF6z — Ernesto Falcon (@EFFFalcon) January 8, 2020

While calling for a vague deescalation, Biden suggested the president's biggest issue was not the war crimes he is committing or threatening to commit, but that Trump "refuses to level with the American people" about the dangers he has created. As numerous critics have noted, Biden—as well as former South Bend, Indiana Mayor Pete Buttigieg—have largely criticized Trump not for his war-mongering, but for being not very good at it.

"Biden would like you to believe that he has seen the light when it comes to the folly of imperialist adventures abroad, that he has found redemption post-Iraq. But his response to the assassination of Soleimani suggests that the old Biden is alive and well." —Meagan Day, Jacobin magazineAs Meagan Day wrote for Jacobin magazine last week, "Biden would like you to believe that he has seen the light when it comes to the folly of imperialist adventures abroad, that he has found redemption post-Iraq. But his response to the assassination of Soleimani suggests that the old Biden is alive and well."

"No," Day concluded, "Joe Biden cannot be relied upon to make the case against Trump's war."

On Tuesday night, meanwhile, just before the Iran missile attack on two military bases where U.S. forces are stationed took place, Sanders appeared on the "PBS NewsHour" and said that the push for war by Trump and top officials in his administration "feels to me exactly what I saw in 2002 and 2003, and that was the leadup and justification for the war in Iraq."

"I opposed that war vigorously and it turned out to be one of the worst foreign policy blunders in the history of United States," Sanders continued. "A war with Iran would likely be even worse."

Live on @NewsHour: Sen. Bernie Sanders comments on the escalated tensions between the U.S. and Iran https://t.co/0iNghsXuQU SCROLL TO CONTINUE WITH CONTENT Never Miss a Beat. Get our best delivered to your inbox.





— PBS NewsHour (@NewsHour) January 7, 2020

In his role as a U.S. Senator, Sanders last week joined with Rep. Ro Khanna (D-Calif.) to introduce legislation that would prevent any funding for a military offensive against Iran without prior congressional authorization.

At a rally taking place in Brooklyn Tuesday night as the news arrived of the Iranian strikes, Warren told the crowd that "the American people do not want a war with Iran"—words that received a standing ovation.

"The American people do not want a war with Iran." —Sen. Elizabeth WarrenAppearing on MSNBC's "Morning Joe" Wednesday morning, Warren said the war in Iraq "was a mistake and I think it was a mistake for anyone to vote for that war."

Asked specifically if Biden made a mistake by voting for the war, Warren simply replied: "Everybody."

Instead of escalating conflict and the growing threat of war, Warren said the goal should be to deescalate the situation and get Iran back to the negotiating table to end hostilities.

WATCH: Sen. Warren calls for negotiating with Iran following Wednesday's retaliation: "We should de-escalate here and try to get Iran back to the negotiating table." https://t.co/JxLip71aX7 pic.twitter.com/mv8Z1MWFKw — MSNBC (@MSNBC) January 8, 2020

Exhibiting their anti-war leadership, both Sanders and Warren are participating in a national strategy call organized by lawmakers and progressive advocacy groups on Wednesday night:

"The American people do not want war with Iran," tweeted Sanders on Wednesday morning, just before Trump was scheduled to address the U.S. public in a televised address. "They want to invest in health care, education, housing, and good jobs. Congress cannot stand by. It must act now to pass our legislation to uphold the Constitution and prevent Trump from spending trillions more on endless war."