Billionaire investor Bill Ackman implores Biden to 'set a real red line' and consider military intervention in Ukraine

• Bill Ackman said on Twitter that President Joe Biden should consider military intervention in Ukraine.
• The investor said he is not advocating for "U.S. boots on the ground today," but said he sees no alternative.

Bill Ackman called for President Joe Biden to consider sending US troops to defend Ukraine in a post on Twitter Monday.

"Is there a point at which we say it is un-American to sit back and watch this transpire?" the billionaire investor said in a series of tweets addressed to Biden. "Do we wait for him to kill millions before we intervene?" Ackman added.

—Bill Ackman (@BillAckman) February 28, 2022

Ackman, CEO of hedge fund Pershing Square Management Capital, appeared to clarify his statements regarding sending US troops into Ukraine in a later post. He said he is not advocating "U.S. boots on the ground today" and that the US should be doing more in the meantime to shut down all Russian banks and continue to provide Ukrainians with weapons and gear.

—Bill Ackman (@BillAckman) February 28, 2022

"We need to set a red line on the use of nuclear weapons to deter their use," Ackman said. "If the unthinkable happens, I see no alternative to our entering the war."

On Thursday, Biden said US troops "will not be engaged in the conflict."

"Our forces are not going to Europe to fight in Ukraine but to defend our NATO allies and reassure those allies in the east," Biden said during the press conference where he announced new sanctions against Russia.

Over the weekend, the US, EU, UK and Canada said they would cut select Russian banks' out of a key global payments messaging system called SWIFT and also sanction the country's central bank — a move that could wreak havoc on Russia's financial system.

Ackman weighed in on the sanctions on Saturday, saying he wouldn't trust Russian banks to stay solvent, following the sanctions.

On Sunday, Russian President Vladimir Putin appeared to threaten the possibility of turning the Ukraine invasion into a broader nuclear conflict when he told top defense and military officials to put nuclear forces in a "special regime of combat duty." Putin blamed the move on statements from member nations of the North Atlantic Treaty Organization (NATO) and from Western nations, which he called "aggressive."

Ackman is not the only investor on Wall Street to say that Russia's aggression toward Ukraine could negatively impact the US. Billionaire investor Ray Dalio has been warning for months that foreign powers could challenge America's global leadership.