As Russia and the US move to negotiate a peace treaty over Ukraine, all eyes are on the relationship between Donald Trump and Vladimir Putin. The two men have seemingly decided to settle things bilaterally; the world’s most nuclear-armed bromance has never felt more consequential.

In a social media post on Wednesday, Trump said he had a “lengthy and highly productive” phone call with Putin, during which they “agreed to have our respective teams start negotiations immediately”.

Later that day, the president told reporters he and Putin would “meet in Saudi Arabia” and that while it was unlikely Ukraine would return to its pre-2014 borders, “some of that land will come back”. Dmitry Peskov, the Kremlin spokesman, said that the Russian president agreed with Trump that it was time to work together.

The surprise conversation came just hours after a prisoner exchange. On Tuesday, Russia released Marc Fogel, an American schoolteacher and former diplomat, who had been serving a 14-year sentence for marijuana possession, in exchange for an unnamed Russian national who had been jailed in the US on money laundering charges.