The head of the EU’s Executive Commission says Russia would face “massive consequences” if they attack Ukraine.

Western powers are preparing sanctions that would limit Russia’s access to financial markets and high-tech goods if they attack Ukraine, a top European Union official said Saturday.

The comments from Ursula von der Leyen, head of the EU’s Executive Commission, came as tensions over Russia’s intentions toward Ukraine intensified. U.S. President Joe Biden said Friday he believed that Russian President Vladimir Putin has decided to invade the neighboring country.

“The Kremlin’s dangerous thinking, which comes straight out of a dark past, may cost Russia a prosperous future,” von der Leyen said Saturday during the annual Munich Security Conference, where U.S. Vice President Kamala Harris also spoke.

Von der Leyen said the EU’s executive arm has developed a “robust and comprehensive package” of possible financial sanctions against Russia with the U.S., U.K. and Canada.

Leveraging Russia’s dependence on western goods and technology

“In case that Russia strikes, we will limit the access to financial markets for the Russian economy and (impose) export controls that will stop the possibility for Russia to modernize and diversify its economy,” she added. “And we have a lot of high-tech goods where we have a global dominance, and that are absolutely necessary for Russia and cannot be replaced easily.”

The EU chief disclosed details of sanctions the EU is preparing. Von der Leyen told Germany’s ARD public television that measures would hit “all goods we make that Russia urgently needs to modernize and diversify its economy, where we are globally dominant and they have no replacement.”

Von der Leyen also said that the EU wouldn’t impose penalties until Russia strikes. “The move to sanctions is so enormous and consequential that we know we must always give Russia a chance to return to diplomacy and the negotiating table,” she said. “This window is still open.”