US billionaire Elon Musk was embroiled in a social media argument Monday with Ukrainian officials, including President Volodymyr Zelenskyy, over his ideas on ending the Russian invasion.

Musk sparked the controversy on Twitter by proposing a peace deal that would include a repeat of UN-supervised annexation referendums in Moscow-held Ukrainian regions, recognition of Russian sovereignty over the Crimean peninsula, and granting Ukraine neutral status.

The Tesla and SpaceX founder created a poll so his more than 107 million followers could vote on the idea.

Zelensky responded with his own Twitter poll, asking, “Which @elonmusk do you like more?” with the options “One supporting Ukraine” and “One supporting Russia.”

Kiev’s ambassador to Germany, Andriy Melnyk, bluntly replied: “My very diplomatic response (to Musk) is to get lost.”

Ukraine’s presidential adviser Mykhaylo Podolyak proposed a “better peace plan” under which Ukraine would retake its territories including Crimea, Russia would be demilitarized and denuclearized, and “war criminals” would be tried by an international tribunal.

Musk later said Moscow could announce full mobilization, which, given Russia’s far larger population, would result in a “full war” in which “death on both sides will be devastating.”

“Victory for Ukraine is unlikely in all-out war. If you care about the people of Ukraine, seek peace,” he wrote on Twitter.

Russian President Vladimir Putin has urged Ukraine to cease hostilities and negotiate after ordering partial mobilization to bolster its armed forces and threatening to use nuclear weapons.

Zelenskyi said he would never negotiate with Russia as long as Putin remains his leader.