The discussion of a summit came amid the countdown to President Trump's Friday deadline for Russia to agree to a ceasefire with Ukraine or face new sanctions and tariffs on Russian energy exports.

Putin and George W. Bush met 28 times during Bush’s two terms. They hosted each other for talks and informal meetings in Russia and the U.S., met regularly on the sidelines of international summits and forums, and boasted of improving ties between onetime rivals.

Russian President Vladimir Putin meeting with U.S. presidents was a regular occurrence early in his tenure. But as tensions grew between Russia and the U.S. through the years, those bilateral gatherings became less frequent.