Donald Trump has chosen oil boss Rex Tillerson as his Secretary of State.

The ExxonMobil chairman and chief executive was described as "one of the truly great business leaders of the world" by the US President-elect in a tweet announcing his decision.

Mr Trump's office said Mr Tillerson would be a "forceful and clear-eyed advocate for America's vital national interests, and help reverse years of misguided foreign policies and actions that have weakened America's security and standing in the world".

Mr Tillerson, 64, has held the top jobs at ExxonMobil since 2006 and was due to retire in March under the company's policy, which sees employees retire at 65.


I have chosen one of the truly great business leaders of the world, Rex Tillerson, Chairman and CEO of ExxonMobil, to be Secretary of State. — Donald J. Trump (@realDonaldTrump) December 13, 2016

The Texan trained as an engineer and has never worked in government so, while he may be experienced at reaching business deals with other nations, he has no experience working with them as a diplomat.

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He is also likely to face a tough confirmation process before the Senate, with issues likely to include his close relationship with Russian President Vladimir Putin and his views on climate change.

Image: Mr Tillerson will face a tough Senate confirmation battle

He first met Mr Putin in the 1990s while supervising an Exxon project on the Russian island of Sakhalin and they became closer after Mr Putin took over from Boris Yeltsin in December 1999.

In 2011, a deal was signed between ExxonMobil and Russia's public energy giant Rosneft to explore and drill in the Arctic and Siberia, a deal that could generate hundreds of billions of pounds.

But after Russia's 2014 incursion into Crimea, US sanctions forced ExxonMobil to scrap some projects and put the Rosneft deal on hold.

During a shareholders' meeting that year, Mr Tillerson voiced his frustration, saying: "We always encourage the people who are making those decisions to consider the very broad collateral damage of who are they really harming with sanctions."

Image: Mr Tillerson's views on foreign policy are not well known

Another issue likely to come up during the oil boss's confirmation battle is climate change.

Mr Tillerson has previously acknowledged that the Earth's climate is changing, the average temperature is rising and greenhouse gases are increasing.

But he has also said that climate remains a complex area of scientific study and, despite an increase in energy production from fracking in the US, he has resisted cutting investment in the search for new oil wells.

The thing I like best about Rex Tillerson is that he has vast experience at dealing successfully with all types of foreign governments. — Donald J. Trump (@realDonaldTrump) December 13, 2016

In 2011, he warned that, should the US step back, a "large consuming country" such as China could "step into that void".

ExxonMobil's scientists recognised climate change as early as the 1970s, according to recently leaked internal documents, and some US states are suing the oil company for allegedly deceiving the public about the role of fossil fuels in global warming.

Mr Tillerson's views on foreign policy are not well known, apart from his support for free trade and American engagement in the Middle East, neither of which fit with Mr Trump's campaign pitches.

After the Iraq War, ExxonMobil agreed to develop a large project in southern Iraq on terms less favourable to the company than most of its other deals.

Mr Tillerson was paid $27.3m (£21.5m) last year and has approximately $160m (£126m) in Exxon stock and $149m (£117m) in uninvested stock options, according to a statement filed by the company with the Securities and Exchange Commission.

Holding these shares could pose a conflict of interest because decisions he might make as Secretary of State - dropping sanctions against Russia, for example - would likely influence that share price.

Mr Tillerson has beat eight or nine contenders for the secretary of state role, including former CIA director David Petraeus, former UN ambassador John Bolton, Senate Foreign Relations chairman Bob Corker and one-time Trump critic and former Massachusetts governor Mitt Romney.