Image copyright AP Image caption Rex Tillerson has been chairman of Exxon Mobil since 2006

Exxon Mobil CEO Rex Tillerson has met President-elect Donald Trump amid growing speculation that he is being considered for US secretary of state.

NBC News quotes sources close to Mr Trump as saying that Mr Tillerson is likely to be named next week.

Former UN ambassador John Bolton will serve as his deputy, NBC adds.

The news comes as Mr Trump's team challenged the accuracy of intelligence reports that Russia intervened to boost his election prospects.

Veteran Republican Mitt Romney is among others who have also also been linked to the role of secretary of state.

Former New York City Mayor Rudy Giuliani withdrew himself from consideration for the post last week. Mr Giuliani's foreign business dealings had raised questions over his suitability.

Mr Tillerson, 64, has extensive experience in international negotiations and a business relationship with Russian President Vladimir Putin.

He has been a critic of the international sanctions against Russia for annexing Crimea.

Under scrutiny: Analysis by Barbara Plett Usher, BBC News, Washington

Image copyright EPA Image caption Mr Tillerson (L) meeting Mr Putin (R) in Russia in June 2012

This is the latest twist in Donald Trump's weeks-long search for a top diplomat: he has been considering close to a dozen candidates with significantly different views and backgrounds.

Transition officials say he has finally settled on Rex Tillerson although there has been no official announcement.

The long-time oil executive does not have any diplomatic experience but he has done business with many foreign governments, including in Russia where he has developed a good relationship with President Vladimir Putin.

That is one reason his nomination would be closely scrutinised by lawmakers - especially in the wake of intelligence assessments that Russian hackers acted covertly to promote Mr Trump's campaign.

Meanwhile, Mr Trump's presidential transition team took issue with CIA assessments that said Russia had attempted to assist Mr Trump during the November election by releasing hacked emails harmful to Democratic candidate Hillary Clinton.

In a statement, the transition team said the officials making the assessment were "the same people that said Saddam Hussein had weapons of mass destruction".

And spokesman Sean Spicer said there were "people within these agencies who are upset with the outcome of the election".