MOSCOW (Reuters) -Russian warplanes were damaged but not destroyed in a June 1 attack by Ukraine, and they will be restored, Russian Deputy Foreign Minister Sergei Ryabkov said. Ukrainian strikes targeted airfields in Siberia and the far north where Russia houses heavy bombers that form part of its strategic nuclear forces.

Russian President Vladimir Putin told President Donald Trump in a phone call Wednesday that he was obligated to respond to Ukraine’s weekend drone attack, Trump said, setting up a potential escalation in the conflict just as the US president hopes to broker an end to the war.