President Joe Biden will issue an executive order soon that will prohibit economic activity between U.S. individuals and the two breakaway regions of eastern Ukraine that Russian President Vladimir Putin recognized as independent entities on Monday, the White House said.

Putin's recognition of the rebel-held areas could pave the way for Moscow to send military forces into the two regions - Donetsk and Luhansk - and argue that it is intervening as an ally to protect them against Ukraine.

"We have anticipated a move like this from Russia and are ready to respond immediately," White House spokesperson Jen Psaki said in a statement. "President Biden will soon issue an Executive Order that will prohibit new investment, trade, and financing by U.S. persons to, from, or in the so-called DNR and LNR regions of Ukraine."

The order will "also provide authority to impose sanctions on any person determined to operate in those areas of Ukraine," Psaki said.

Psaki said more measures were forthcoming and said these were separate from sanctions that the United States and its allies have been preparing if Russia invades Ukraine.

"To be clear: these measures are separate from and would be in addition to the swift and severe economic measures we have been preparing in coordination with Allies and partners should Russia further invade Ukraine," she said.

The EU is said to be planning sanctions as well. 

And on Monday afternoon, Britain's foreign minister, Liz Truss, said her government would announce sanctions on Russia over the recogition of the breakaway regions by Putin on Tuesday. "Tomorrow we will be announcing new sanctions on Russia in response to their breach of international law and attack on Ukraine's sovereignty and territorial integrity," Truss said on Twitter.

Biden, who convened a meeting with his national security team at the White House earlier in the day, held a 35-minute call with Ukrainian President Volodymyr Zelenskyy and had a call with French President Emmanuel Macron and German Chancellor Olaf Scholz.

"We are continuing to closely consult with Allies and partners, including Ukraine, on next steps and on Russia’s ongoing escalation along the border with Ukraine," Psaki said.