“We will miss her knowledge, experience and leadership skills,” his statement said.

The head of the State Department thanked Thompson for the work, without specifying the reasons for the resignation.

Thompson was the United States' chief negotiator on strategic stability at meetings with Russia.

She participated in consultations with Deputy Foreign Minister Sergei Ryabkov. In particular, they concerned the Treaty on the Elimination of Intermediate-Range and Shorter-Range Missiles, from which the United States withdrew in August.