President Donald Trump is moving to name Fiona Hill, a former intelligence officer and well-known scholar of Russian President Vladimir Putin, as his top Russia adviser, according to a person familiar with the matter.

Hill, a senior fellow at the Brookings Institution who worked at the National Intelligence Council from 2006 to 2009, is in line to become White House senior director for Europe and Russia, said the person, who asked not to be identified because the appointment hasn’t been made official. The person said Hill “wrote the book” on Putin, a reference to “Mr. Putin: Operative in the Kremlin,” a 2013 biography of the Russian leader.

The White House offered Hill the job before National Security Adviser Michael Flynn resigned for misleading Vice President Mike Pence about the nature of his contacts with Russian Ambassador Sergey Kislyak in the days after Trump’s victory, according to the person.

Hill declined to comment on her selection, which was reported earlier by Foreign Policy magazine, when reached by text message on Thursday. Hill was a national intelligence officer for Russia and Eurasia at the National Intelligence Council, serving under both George W. Bush and Barack Obama.

Hill’s appointment is likely to reassure critics who have said Trump may take too soft a line toward Russia and seek to improve ties at the expense of European allies and the NATO alliance. In an essay she co-authored in October, Hill advocated keeping sanctions in place over Russian aggression in Ukraine and rejected the idea of a “grand bargain” with Putin in which the U.S. would trade concessions in Ukraine for Russian help in the Middle East.

"Great hire,” said Michael McFaul, U.S. ambassador to Russia under Obama. "Fiona is both a first-class scholar on Russia and an experienced former government official.”

Trump said before his election that he might lift the U.S. penalties imposed over Russia’s annexation of Crimea and support for separatists in eastern Ukraine. But optimism in Moscow has slowly faded that Trump’s presidency will mark a new era of cooperation as the new administration has refused to lift sanctions imposed by President Barack Obama and continued to challenge Putin over his alliance with Syria’s President Bashar al-Assad.