U.S. Defense Secretary Ashton Carter said Monday that economic sanctions are having an effect in answering Russian “aggression” in Ukraine. He also said there is neither a desire for a return to Cold War tensions nor for a new conflict with Russia.

Secretary Carter spoke at a conference in Berlin, where he met with Germany’s defense minister. He added that while the West is not looking to be enemies with Russia, it will defend itself if necessary.

The U.S. official will travel Tuesday to Estonia for meetings with the defense ministers of Estonia, Latvia and Lithuania. All three countries were once under the influence of the government in Moscow and the Soviet Union.