The summit has not been set in stone, but if Russia's Vladimir Putin does go to Budapest to meet US President Trump in the next two weeks, he would need to clear a few hurdles first.
When Putin travelled to Alaska for his Anchorage summit in August, the US granted special permission for the presidential plane - a modified Ilyushin Il-96 airliner dubbed the "Flying Kremlin" that has four engines and is bristling with defence systems.
Russian planes are banned from US air space, and from EU air space too. So if Putin does fly to Budapest he would need special dispensation if he decided to fly over an EU member state.
It is perfectly possible, but landlocked Hungary is not the easiest destination to get to for a Russian president who rarely sets foot abroad and has not travelled to the EU for years.
"For now, of course, it's not clear," says Kremlin spokesman Dmitry Peskov. "What we do have is the willingness of the presidents to hold such a meeting."
