White House national security adviser Jake Sullivan said Tuesday that President Biden and U.S. allies would announce new sanctions on Russia for its invasion of Ukraine when the president travels to Brussels later this week.  

“He will join our partners in imposing further sanctions on Russia and tightening the existing sanctions to crack down on evasion and to ensure robust enforcement,” Sullivan told reporters during a press briefing.  

Sullivan declined to provide details about specific sanctions, saying he wouldn’t get ahead of the announcement that would be made in conjunction with U.S. allies on Thursday.  

Still, he emphasized that the measures would involve enforcing current sanctions by “ensuring that there is joint effort to crack down on evasion, sanctions busting, on any attempt by any country to help Russia basically undermine, weaken, or get around the sanctions.” 

Biden is slated to attend an emergency NATO meeting, met with the other Group of Seven (G-7) leaders, and address a European Council summit on Thursday in Brussels. He’ll also travel to Poland and meet with Polish President Andrzej Duda the following day.  

Sullivan also said that Biden would announce a new joint action on enhancing European energy security as well as new U.S. contributions to a humanitarian response to Russia’s war in Ukraine. Millions of Ukrainians have fled their homes amid the war, many of them crossing over into neighboring Poland. It’s unclear if Biden will meet with refugees when he visits Poland on Friday.

The U.S. and its allies have already imposed punishing sanctions on Russia over its invasion of Ukraine that began almost four weeks ago. These measures include sanctions on Russian banks and oligarchs and the removal of some Russian banks from the SWIFT international banking system.

Biden has also banned domestic Russian oil and gas imports, a step that Europe did not join in because of its dependence on Russian energy.