President Joe Biden left the White House early Wednesday for a trip that will include talks in Brussels with NATO and European leaders to discuss additional sanctions on Russia in the wake of its invasion of Ukraine.
Two sources familiar with the situation said Biden and his team were developing plans to impose sanctions on members of the Russian parliament, the Duma, which are expected to be announced on Thursday.
The Wall Street Journal said 300 members of the Duma could face sanctions.
A White House spokesperson said "no final decisions have been made about who we will sanction and how many we will sanction."
"We will have additional sanctions measures to announce that will rolled out in conjunction with our allies on Thursday when the president has the opportunity to speak with them," the official said.
White House national security adviser Jake Sullivan told reporters on Tuesday that Biden will attend an emergency NATO summit on Thursday, meet with G7 leaders and address the 27 leaders of the European Union at a session of the European Council.
Biden will coordinate on the next phase of military assistance to Ukraine, said Sullivan.
In addition to imposing fresh sanctions on Russia, Biden will work with U.S. allies to tighten existing sanctions to "crack down on evasion and to ensure robust enforcement," Sullivan said.
Biden has vowed not to engage in direct conflict with Russia but has pledged the United States will defend all NATO territory. He has ordered more U.S. troops to NATO's eastern flank to reassure those edgy allies.
During his visit to Poland, Biden will visit U.S. troops and meet with experts involved in the humanitarian response to helping hundreds of thousands of Ukrainians who have fled their country and those who remain there.