The White House explained Thursday why US President Donald Trump imposed sanctions on Russia’s oil sector this week.

The new sanctions target two of Moscow’s largest energy companies, Rosneft and Lukoil, freezing their US-based assets and barring American companies from doing business with them.

White House Press Secretary Karoline Leavitt said Trump “has always maintained that he would implement sanctions on Russia when he felt it was appropriate and necessary, and yesterday was that day.”

“I think the President has also long expressed his frustration with Vladimir Putin and, frankly, with both sides of this war. He has always said that in order to negotiate a good peace deal, both sides need to be interested in a good peace deal. And he feels as though, unfortunately, from the Russian side as of late, he has not seen enough interest or enough action in terms of moving the ball forward towards peace,” Leavitt said.

The move marks the first major sanctions on Russia since Trump returned to office, following concerns that Moscow has not demonstrated sufficient willingness to engage in negotiations to end the war in Ukraine.