US President-elect Donald Trump is to pick Exxon Mobil chief executive officer Rex Tillerson as secretary of state in his upcoming administration, officials have said. Trump tweeted on Monday evening (12 December) that he would be announcing the decision on Tuesday morning.

Tillerson beat a competitive field including former Massachusetts governor and Republican presidential candidate, Mitt Romney, who posted on Facebook that "It was an honor to be considered for Secretary of State" and added that he had "very high hopes" for the upcoming administration.

Tillerson's confirmation in the Senate is not set to be an easy ride, with some already calling into question the oil chief's links to Russia and his personal relationship with its leader Vladimir Putin. Republican Senator and another former GOP presidential candidate, John McCain has called Tillerson's relationship with Putin "a matter of concern".

Another potential pick was former New York mayor Rudy Giuliani, an avid Trump backer from early in the campaign. Giuliani had been publicly lobbying for the secretary of state job but was reportedly offered lesser roles that he turned down. On Friday, the transition team sent out a statement saying that Giuliani had "removed his name from consideration for a position in the new administration".

Exxon Mobil Chairman and CEO Rex Tillerson
Exxon Mobil Chairman and CEO Rex Tillerson, shown here testifying before a congressional committee in 2010 Reuters