The White House is discussing a plan to oust Secretary of State Rex Tillerson and replace him with CIA director Mike Pompeo in a major shake-up of President Donald Trump's national security team, two administration officials have said.

Donald Trump has challenged Rex Tillerson to "compare IQ tests" if his secretary of state called the president a "moron", as reported.

US secretary of state Rex Tillerson has offered reassurance to North Korea that "we are not your enemy".

The Treasury Department has fined Exxon Mobil $2m for violating Russia sanctions while Secretary of State Rex Tillerson was the oil company's CEO.

Russian President Vladimir Putin is meeting with US Secretary of State Rex Tillerson at the Kremlin in Moscow.

US Secretary of State Rex Tillerson has said he aims to clear up "sharp differences" with Moscow as he opened a tense meeting with Russian Foreign Minister Sergey Lavrov.

US secretary of state Rex Tillerson has said Russia must abide by a 2015 deal aimed at ending fighting between Ukrainian forces and Russia-backed separatists.

President-elect Donald Trump has confirmed his choice of Rex Tillerson to be his secretary of state, hailing him as "among the most accomplished business leaders and international deal makers in the world".