But over the past few years Mr Rubio has softened some of his stances to align more closely with Mr Trump's views - so much so that he was one of three final contenders for Mr Trump's vice-presidential pick for this term, eventually losing out to JD Vance.
File pic: Reuters] Mr Rubio, a former Florida senator, already spoke to Russian foreign affairs minister Sergey Lavrov over the phone on Saturday, discussing the war in Ukraine and other topics, according to readouts of the call from both countries.
Mr Witkoff, Mr Trump's special Middle East envoy, is a long-time friend of the president's and a fellow billionaire real estate developer.
Mr Witkoff has been busy in his new Middle East role, having been Mr Trump's man in the room for the extremely fragile Israel-Hamas ceasefire negotiations.
Before his appointment in Mr Trump's cabinet, he co-wrote an article in The Economist that laid out his view of how the US could move to convince Russia to end the war: either by offering to ease sanctions or threatening greater assistance to Kyiv.
