Rex Tillerson was director of US-Russian oil firm

US President-elect Donald Trump’s pick for America's next secretary of state was a director of a Bahamas-based US-Russian oil company, a leaked document shows.

Rex Tillerson had been former director of ExxonMobil’s Russian subsidiary, Exxon Neftegas, based in the tax haven of the Bahamas, according to the document.

The document was part of 1.3 million files given to the German newspaper Suddeutsche Zeitung by an anonymous source.

Tillerson is the chairman and chief executive officer (CEO) of ExxonMobil, the largest oil company in the world. He became a director of Exxon Neftegas in 1998, according to the leaked 2001 document, which came from the corporate registry in the Bahamas.

Tillerson has reportedly close business relations with Russia and was awarded “Order of Friendship” -- one of the country’s most prestigious awards given to foreign nationals -- by the Russian government in 2013.

Under Tillerson’s management, the energy giant ExxonMobil negotiated a major energy deal with Moscow in 2011, according to The Wall Street Journal. Putin said at the time that the deal could be worth over $500 billion.

Tillerson’s Russia ties have become a source of bipartisan concern. His appointment must be approved at the Senate Foreign Relations Committee where Republicans hold a 10-to-nine advantage.

If just one Republican member and all Democrats gang up against Tillerson, they could sink his nomination before it even reaches the Senate floor.

Two Republican senators in the committee – Marco Rubio and John McCain – have already questioned the ExxonMobil CEO’s close business ties with Russia and its President Vladimir Putin.

According to reports, in a meeting with Trump, Robert Gates, former CIA director and defense secretary, personally recommended Tillerson for the post of secretary of state.

While former secretary of state Condoleezza Rice made the same recommendation during her meeting with Vice President-elect Mike Pence.

Both Gates and Rice run a consulting firm that considers ExxonMobil among its clients.

Meanwhile, former US vice president Dick Cheney has been a vocal supporter of the ExxonMobil chief, describing his nomination as an “inspired choice.”

The Washington Post reported on Friday that Cheney was reportedly lobbying on behalf of Tillerson. The 75-year-old neoconservative politician spoke to Senator Rubio and some other senators in order to get their support for the oil chief’s confirmation from the Senate.