WASHINGTON — Texas oilman Rex Tillerson was set to meet Tuesday with President-elect Donald Trump — a late entrant into the high-stakes jockeying for secretary of state, and one whose close ties to Russia have raised eyebrows.

As head of Exxon Mobil, the world's 8th largest company, Tillerson has plenty of negotiating experience and face time with world leaders -- though limited experience when it comes to the gamut of issues the nation's chief diplomat deals with.

He's under pressure for ties with Russian leader Vladimir Putin, especially given questions about the president-elect's outspoken admiration for the Russian strongman.

Environmentalists and Democrats say they relish the prospect of confirmation hearings that put the head of an oil giant under oath.

"There are plenty of other candidates for secretary of State who don't bring that kind of baggage to the table and would not engender that kind of firestorm at confirmation hearings," Peter Frumhoff, director of science and policy at the Union of Concerned Scientists, told Politico. "Of the candidates I've seen, none would fare worse than Rex Tillerson."

Senate Democrats see a Tillerson nomination as an opening to grill him over allegations that Exxon suppressed internal research about climate change and, in particular, the impact of fossil fuels on climate.

Just over a year ago, New York Attorney General Eric Schneiderman launched a probe into whether Exxon misled investors, regulators, and the public about its climate research since the late 1970s. Massachusetts and the Virgin Islands also opened investigations.

"Covering up climate science and deceiving investors qualifies you for federal investigation, not federal office," said May Boeve, executive director of 350.org, an environmental group. "An oil baron as Secretary of State would do enormous damage. Tillerson could deeply disrupt international efforts towards climate action, take retribution against countries that defy the oil industry, and help write more international trade deals that put profit ahead of people and planet."

Tillerson apparently entered and left Trump Tower without passing journalists camped out in the main lobby. Trump aides said his appointment was in the morning.

Trump had focused on four candidates for secretary of state: Mitt Romney; former New York City Mayor Rudy Giuliani; Senate Foreign Relations Chairman Bob Corker of Tennessee; and retired Gen. David Petraeus.

Romney, the party's 2012 nominee, was among Trump's harshest critics during the primaries. They met twice in recent weeks and apparently hit it off -- triggering backlash from Trump campaign manager Kellyanne Conway and other loyalists who view the post as too big a prize for someone who tried to block Trump's ascent.

Amid the squabbling, reports surfaced this weekend that Trump broadened the search to include John Bolton, a United Nations ambassador under President George W. Bush; former Utah Gov. Jon Huntsman Jr., a Republican who speaks some Mandarin and served as ambassador to China under President Barack Obama; West Virginia Sen. Joe Manchin, a Democrat; and Tillerson.

Huntsman called on Trump to drop off the ticket in October, after the revelation of a vulgar "Access Hollywood" tape on which Trump bragged about groping women. Over the weekend, he defended Trump's precedent-breaking phone call with the president of Taiwan, which angered mainland China.

Irving-based Exxon, with operations in 50 countries and on six continents, is the largest company with headquarters in Texas, and the eighth largest in the world by revenue. Tillerson joined the company as an engineer in 1975 after graduating from the University of Texas, and he's led the company since 2006.

Tillerson faces mandatory retirement when he turns 65 in March.

He reportedly owns $151 million worth of Exxon shares. Ethics laws likely would force him to sell to avoid conflicts of interest. But like other wealthy cabinet picks, he would enjoy a huge windfall because of an obscure law that eliminates the tax bite when federal appointees are forced to divest holdings.

Trump's election could lead to a dramatic pivot in U.S.-Russian relations, which soured after Russia annexed Ukraine's Crimea region in 2014. U.S. intelligence officials blame Russia for hacking into Democratic Party emails to interfere with the presidential election.

Few Americans are closer with Putin than Tillerson, who has long represented Exxon's interests in Russia.

"He has had more interactive time with Vladimir Putin than probably any other American with the exception of Henry Kissinger," John Hamre, a deputy defense secretary during the Clinton administration and president of the Center for Strategic and International Studies, a Washington think tank where Tillerson is a board member, told the Wall St. Journal.

In 2011 Exxon beat out BP and other competitors in a historic deal giving it access to Arctic and other deposits in Russia, while allowing state-owned Rosneft its first-ever access to energy projects in the United States. The next year, "the Kremlin bestowed the country's Order of Friendship decoration" on Tillerson, the Journal reported.

But as Bloomberg recounted, "shortly after the venture discovered a billion-barrel crude field in the Kara Sea, the U.S. and European Union imposed sanctions" after Russia's invasion of Crimea. Lifting those sanctions would hit Exxon's bottom line.