Rex Tillerson, the ExxonMobil chief who is President-elect Donald Trump’s nominee for secretary of state, visited the White House repeatedly as sanctions were imposed on Russia in 2014 to make sure his company’s competitors didn’t gain an edge in the way they were enforced.

Tillerson made at least 20 visits to the White House during President Barack Obama’s two terms, visitor logs show, including five after Obama began authorizing the 2014 sanctions in response to Russian aggression toward Ukraine.

Tillerson, who has questioned whether sanctions work, was concerned that European nations might not apply the restrictions as strictly as the U.S., giving Exxon’s European competitors an advantage, according to a White House official at the time, who asked not to be identified because the purpose of the visits was never made public.

As secretary of state, Tillerson would play a central role in deciding whether and how to maintain the current sanctions regime against Russia. Hundreds of people including Igor Sechin, the president of Russian oil giant Rosneft PJSC — Exxon’s partner in Russia — are targeted under the U.S.’s sanctions over President Vladimir Putin’s intervention in Ukraine.

“White House officials regularly meet with business leaders from a wide range of industries to discuss policy issues,” White House spokeswoman Jennifer Friedman said in an email. “These meetings help keep the White House apprised of outside perspectives.”

At Exxon’s May 2014 shareholder meeting, Tillerson said of sanctions: “We don’t find them to be effective unless they are very well implemented.”

Members of Congress have signaled that Tillerson’s close relations with Putin will bring tough questions in his Senate confirmation hearing to serve as the top U.S. diplomat. Republican senators including John McCain and Marco Rubio have joined Democrats indicating they would press Tillerson on issues such as sanctions.

The Exxon chairman and chief executive officer met several times with Jeffrey Zients, director of the National Economic Council, according to to the White House logs. Those visits began on March 12, 2014, six days after Obama signed Executive Order 13660, authorizing sanctions such as travel restrictions on people and entities deemed responsible for violating the sovereignty and territorial integrity of Ukraine, or stealing assets of the Ukrainian people. Tillerson and Zients met two more times in 2014 and twice in early 2015.

Exxon signed a strategic cooperation agreement with Rosneft in 2011, and in 2014 the companies together drilled an exploration well in Arctic waters. When the Obama administration imposed sanctions later that year, Exxon successfully lobbied the administration to give it a two-week reprieve to keep working on the $700 million well in the Kara Sea long enough to cap it for an eventual return. Exxon persuaded U.S. Treasury and Energy Department officials that it couldn’t safely obey the White House order to halt work by the deadline.

Sanctions against Russia remain an issue for the White House and Congress. In October, at the request of the White House, the State Department weighed options for adding more sanctions against Russia over its participation in the siege of the Syrian city of Aleppo. No further action has been taken.

Senators including Rubio have called for more sanctions that would target Russia, not fewer. Last week, Rubio introduced legislation targeting foreigners who threaten order in Iraq and Syria.

“Russia and Iran have continued to bolster and prop up the brutal Assad regime in Syria, which has fueled a conflict that now threatens us here at home,” Rubio said in a Dec. 8 news release.

(c) 2016, Bloomberg · Nick Wadhams, Margaret Talev