Elon Musk says he has not spoken with Vladimir Putin since the Russian president sent his troops into Ukraine. But the billionaire’s warm words for a tweet from a top Kremlin official drew him into an unusual back-and-forth over the war.

The SpaceX Chief Executive Officer praised a snarky post by Dmitry Medvedev on Thursday about the UK Prime Minister Liz Truss, known for her tough stance against Russia’s invasion and strong support for Ukraine.