Secretary of State Marco Rubio has appointed a former member of his Senate staff who primarily has experience as a business consultant as the U.S. State Department’s top official for Europe, according to an internal email sent on Friday seen by Reuters and two officials.

The change in the most senior official who helps oversee U.S. ties with Europe at the State Department comes at a time when Washington is managing an increasingly tense relationship with the continent as President Donald Trump says he wants to take over Greenland, pressure allies on NATO spending and end Russia’s war in Ukraine.