WASHINGTON: President-elect Donald Trump will announce Exxon-Mobil Corp's Rex Tillerson as his choice for secretary of state on Tuesday, a senior transition official said, confident that the oil executive can get past questions about his ties to Russia.

Trump is to make the announcement on Tuesday morning, going with a business leader whose experience in diplomacy is from making deals with foreign countries for the world's largest energy company.

Trump picked Tillerson, 64, after the Texan was backed by several Republican establishment figures including former Secretary of State James Baker, former Secretary of State Condoleeza Rice and former Defense Secretary Robert Gates, the transition official said.

Their backing is seen as key to helping Tillerson get past a possibly contentious Senate confirmation battle that is likely to focus on his relationship with Russian President Vladimir Putin.

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

Trump judged in making the pick that Tillerson could adequately address questions about his ties to Russia, an official said.

Lawmakers 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 who has voiced hawkish views on Iraq and Iran.

Separately, a source close to the transition said Trump had chosen former Texas Governor Rick Perry as his nominee for energy secretary, with an announcement expected soon. Perry met Trump on Monday at Trump Tower in New York.

Republicans and Democrats said Tillerson, who is president of Exxon Mobil Corp, would be asked about his ties to Russia, having met Putin several times. He won fresh praise from Moscow on Monday.

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."

The pick comes amid controversy over the role that alleged Russian cyber hacking may have had on the outcome of the November 8 presidential election.

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While busily filling out his Cabinet, Trump is seeking to answer questions about how he will separate himself from his far-flung business empire before taking over the presidency on Jan. 20.

He had planned a news conference on Thursday to lay out the details but delayed it on Tuesday due to what aides said was the crush of picking people to serve in his administration.

In a series of late-night tweets on Monday, Trump said he will be leaving his business before Jan. 20 so he can focus full-time on the presidency and that he would leave his two sons, Donald Trump Jr and Eric Trump, to manage it.

He did not mention his daughter, Ivanka, who has been a central player in Trump's business affairs and who is said to be considering a move to Washington to help her father.

"No new deals will be done during my term(s) in office," Trump said.

He said he would hold a press conference "in the near future to discuss the business, Cabinet picks and all other topics of interest. Busy times!"

Trump chose Tillerson over 2012 Republican presidential nominee Mitt Romney, who had famously criticized Trump during the party's fight for a nominee this year. Trump called Romney to tell him he had decided to choose someone else for the job.

"It was an honor to have been considered for secretary of state of our great country," Romney said in a Facebook posting on Monday night.

"My discussions with President-elect Trump have been both enjoyable and enlightening. I have very high hopes that the new administration will lead the nation to greater strength, prosperity and peace," he said.