US media say Donald Trump to name Exxon Mobil chief Rex Tillerson, known for his close ties to Russia, as top diplomat.

President-elect Donald Trump has tapped ExxonMobil chief Rex Tillerson as his secretary of state, US media reported, setting up what are likely to be contentious confirmation hearings over his ties to Russia.

“I will be making my announcement on the next Secretary of State tomorrow morning,” Trump said on Twitter on Monday evening.

News outlets including The New York Times, Washington Post and NBC News cited sources as saying he had settled on Tillerson after a drawn-out and public search for the nation’s top diplomat.

INFOGRAPHIC: Who’s who in Donald Trump’s administration?

Trump met Tillerson in New York on Saturday.

Others being considered for secretary of state were former New York Mayor Rudy Giuliani – who took himself out of the race last week – and 2012 Republican presidential nominee Mitt Romney, who posted on Monday evening that he would not be taking the position.

It was an honor to have been considered for Secretary of State of our great country. https://t.co/FC9tB7rdoy — Mitt Romney (@MittRomney) December 13, 2016

Trump called Republican Mitt Romney to tell him he would not get it, CNN reported.

Politicians from both major parties have raised questions about Tillerson and former UN Ambassador John Bolton, who has been mentioned as a possible No 2 State Department official and has voiced hawkish views on Iraq and Iran.

Republicans and Democrats said Tillerson, who is also president of Exxon Mobil Corp, would be asked about his ties to Russia, having met President Vladimir Putin several times.

In 2013, Putin bestowed a Russian state honour, the Order of Friendship, on Tillerson, citing his work “strengthening cooperation in the energy sector”.

‘Friend of Vladimir’

Senator John McCain, a leading foreign policy voice and 2008 Republican candidate for president, told Reuters in an interview: “I have concerns. It’s very well known that he has a very close relationship with Vladimir Putin.”

Calling Putin “a KGB agent who is bent on restoring the Russian Empire”, McCain said in the interview that he would await confirmation hearings if Tillerson is nominated before making a judgment on the nomination.

Another Republican, Senator Marco Rubio, who serves on the Senate Foreign Relations Committee which would review a Tillerson nomination, has voiced similar worries.

Being a "friend of Vladimir" is not an attribute I am hoping for from a #SecretaryOfState – MR — Marco Rubio (@marcorubio) December 11, 2016

Renewed allegations of Russian hackers meddling in the November 8 election, coupled with Trump’s stated admiration of Putin, have stoked concern. Washington is at odds with Moscow over a range of issues that include Syria, Ukraine and NATO’s presence in Eastern Europe.

During Trump’s presidential campaign, Democrats and longtime government officials voiced alarm when Trump repeatedly praised Putin.

American intelligence previously linked Russia to damaging email leaks from the Clinton campaign, but saw it as a broad effort to undermine confidence in the US political process.

On Friday, however, The Washington Post reported that the CIA has since concluded that the aim of the cyber intrusions was to help Trump win.

The report came on the heels of President Barack Obama’s order to review all cyberattacks that took place during the 2016 election cycle, amid growing calls from Congress for more information on the extent of Russian interference.

Separately, Trump is delaying a news conference originally planned for Thursday about his global business dealings until January, top adviser Kellyanne Conway told CNN, as critics point to myriad potential conflicts of interest.

She attributed the delay to “how convoluted and complex many of these business holdings are”, adding that Trump still intends to relinquish operational control of his company while serving as president.

“He’s just a man who’s been incredibly successful and has holdings all across the globe.”