President-elect Donald Trump announced Rex Tillerson as his nominee for secretary of state. Here's what you need to know about Tillerson. (Thomas Johnson,Victoria Walker,Danielle Kunitz/The Washington Post)

President-elect Donald Trump has picked as his secretary of state Rex Tillerson, the chief executive of ExxonMobil, Trump’s transition team announced Tuesday, setting up a possible confrontation with members of his own party in the Senate.

Since Tillerson’s name emerged as a candidate for the post, leading Republicans have expressed reservations about his years of work in Russia and the Middle East on behalf of the multinational oil company. But some lawmakers seemed to be signaling they will support him after the announcement was made.

Also under scrutiny is Tillerson’s ties with Russian President Vladi­mir Putin amid wider probes of Russian influence following a CIA assessment pointing to Russian computer hacking during the presidential race.

After Tillerson’s nomination was official, several Republican senators offered various degrees of support, led by Senate Majority Leader Mitch McConnell (R-Ky.). He said in a statement: “I look forward to supporting his nomination.”

ExxonMobil CEO Rex Tillerson in 2015. (Evan Vucci/AP)

Other GOP senators, including Jeff Flake (Ariz.), who sits on the Senate Foreign Relations Committee that will first have to approve Tillerson before a Senate floor vote, said that backing for Tillerson from some prominent figures — former secretaries of state James Baker and Condoleezza Rice, and former defense secretary Robert M. Gates — “carry considerable weight.”

Foreign Relations Committee Chairman Bob Corker (R-Tenn.) has called Tillerson a “very impressive individual.”

The one obvious red flag for Tillerson is Sen. Marco Rubio (R-Fla.), who is also a member of Foreign Relations, where only one Republican vote would endanger the nomination. Rubio expressed “serious concerns” and vowed to ensure a “thorough” vetting of the nominee on the committee.

“The next secretary of state must be someone who views the world with moral clarity, is free of potential conflicts of interest, has a clear sense of America’s interests,” Rubio said.

Sen. James Lankford (R-Okla.) echoed Rubio’s call that Tillerson’s views be “closely examined,” such as his relations with China and Russia and views on Middle East tensions.

And Sen. Lindsey O. Graham (R-S.C.), who wants a bipartisan investigation of Russian influence on the U.S. elections, said he expects “U.S.-Russia relations to be front-and-center in his confirmation process.”

While Senate Democrats cannot filibuster Trump’s Cabinet picks, Republicans have only 52 votes in the Senate, leaving them in potential jeopardy if Democrats unite in opposition to Tillerson. It will take at least 50 votes to confirm a nominee, plus Vice President-elect Mike Pence casting a tiebreaking vote.

Sen. Charles E. Schumer (D.-N.Y.), the Democrat’s incoming Senate leader, urged that Tillerson face several rounds of questioning over issues such as his “disturbing opposition” to sanctions on Russia and “how he views Putin.”

Like others in the new Trump Cabinet, the ExxonMobil chief executive lacks any experience in government but will try to apply his experience in the business world to the realm of diplomacy. And he has worked extensively around the globe and built relationships with such leaders as Putin.

The Trump team is planning an aggressive public relations campaign to win confirmation for Tillerson and dispel what it sees as a false narrative about his ties to Russia, a person involved in the transition said.

In a statement, Trump called Tillerson an “embodiment of the American Dream” and cited the oil executive’s “tenacity, broad experience and deep understanding of geopolitics.” Trump, however, made no mention of the nomination process in the announcement.

Gates, whose firm Rice Hadley Gates Consulting has ExxonMobil as one of its clients, was the first person to raise Tillerson as a secretary of state possibility with Trump during a meeting at Trump Tower, the transition official added.

Trump did not know much about Tillerson but started chewing over the idea. He invited Tillerson for a meeting, and the two global dealmakers hit it off. They recognized similarities in each other, and the more they talked, the more they liked each other, the transition official said.

Tillerson “would bring to the position vast knowledge, experience and success in dealing with dozens of governments and leaders in every corner of the world,” Gates said in a statement, which did not cite any specific countries.

Rice also did not mention Russia or other nations in her statement of support, but appeared to answer potential critics of Tillerson by calling him a “patriot” who would “represent the interests and values of the United States.”

Rice, who has served on the board of Chevron, spoke with Trump about Tillerson by phone Monday as Trump made his final decision.

One argument that the defenders of Tillerson will probably make is that he stands firm in business negotiations in Russia and elsewhere. During his career, he has also cultivated leaders of countries such as Saudi Arabia, Yemen and Qatar.

“One of the things I know about the Russian government: I’m very predictable. And they know if I say no it means no. And talking about it more isn’t going to change that. No is still going to be no,” Tillerson said in a talk last year at the Texas Tech business school. “Over the years we’ve earned each other’s respect. Then when you say yes, you know we’ll follow through. It means something.”

Weighing whether to lift economic sanctions on Russia will be one of the first things on Tillerson’s plate, given Trump’s desire to smooth relations with the Kremlin. International economic sanctions, imposed after Russia annexed Crimea and gave support to insurgents in Ukraine’s eastern provinces, have fallen heavily on financial institutions and ExxonMobil.

ExxonMobil, which has a profitable operation on Sakhalin island in eastern Russia, had begun a drilling program in the Arctic’s Kara Sea, where Exxon made a find, and had agreed to explore shale oil areas of West Siberia and deep waters of the Black Sea. If sanctions are lifted, Tillerson told analysts this year, the Black Sea drilling would probably be the first to be restarted.

While ExxonMobil complained privately to the Obama administration about the sanctions, the company has abided by the law.

“They understand the situation. We understand the situation,” Tillerson said of the Kremlin when asked at an oil analysts’ meeting this year about whether Exxon would resume work in Russia if sanctions were lifted.

In addition, Tillerson will have to deal with climate issues because the State Department is the lead agency in international climate negotiations. Unlike Trump, Tillerson has said he believes that climate change is real and has favored a revenue-neutral carbon tax of more than $20 a ton.

But environmental groups charge that Exxon knew about the harmful effects of fossil fuels as much as 40 years ago and failed to inform investors and the public, possibly in violation of securities laws. The New York and Massachusetts attorneys general and a range of nongovernmental organizations are locked in battle over the charges.

Human rights experts are also unhappy about Tillerson’s nomination, noting that ExxonMobil does business in countries ruled by autocrats or dictators, including countries in the Middle East, as well as Equatorial Guinea and Kazakhstan.

“I don’t think that companies’ role is to play politics,” said Pavel Molchanov, oil analyst at the investment firm Raymond James. “They’re there to invest in resources. Saying that he personally has some special feelings toward Russia just because Exxon has invested there is probably overstating the case.”

But that might not be the way lawmakers see it.

At least four Republican senators have already publicly expressed their concerns with Tillerson’s Russia ties.

Graham called the fact that Putin awarded Tillerson the Kremlin’s Order of Friendship in 2013 “unnerving,” while Sen. John McCain (Ariz.) questioned Tillerson’s judgment on CNN on Monday noting, “I don’t see how anybody could be a friend of this old-time KGB agent,” referring to Putin.

Established in 1994 by the president at the time, Boris Yeltsin, the Order of Friendship has been handed out by Russian leaders to figures as diverse as pianist Van Cliburn, former Cleveland Cavaliers coach David Blatt, and Raymond E. Johnson, founder of the Museum of Russian Art in Minneapolis.

Earlier Monday, Kremlin spokesman Dmitry Peskov acknowledged Tillerson’s relationship with Putin and his friendly attitude toward Russia, but played down the idea that it would influence policy.

“As to the allegations of whether his attitude to the Russian Federation is good or bad: being secretary of state is very different from leading a company, even a very big one. Therefore, any, so to speak, sympathies become secondary,” Peskov was quoted by the Interfax news agency as telling reporters.

“The only thing that remains here is readiness to demonstrate a constructive attitude and be professional,” he said. “We are hoping that this is what will happen.”

Peskov said Tillerson and Putin have met on several occasions, but the spokesman offered only measured comments about their relationship.

“Indeed, [Tillerson] repeatedly had contacts with our representatives due to his work in the post of one of the world’s largest oil companies; he fulfills his duties very professionally,” Peskov said.

David Filipov in Moscow, and Paul Kane, Anne Gearan and Brian Murphy in Washington contributed to this report.