(CNN) - The State Department's top official for arms control will depart her post next month after months of controversy, triggered by the revelation that she had not disclosed a close relationship she once had with the former boyfriend of Russian agent Maria Butina.
Andrea Thompson is leaving as the Trump administration continues to seek a major nuclear deal with Russia and China after the collapse of the Intermediate Range Nuclear Forces Treaty. The multilateral deal has shown no signs of progress.
Secretary of State Mike Pompeo announced Thompson's departure in a statement on Friday.
"Under Secretary for Arms Control and International Security Andrea Thompson is a dedicated public servant who brought over 25 years of military experience to her role at the State Department," Pompeo wrote. "Her wealth of knowledge, experience, and leadership skills will be missed. I thank her for her commitment to the State Department's mission and for her decades of service to the United States of America. I wish her all the best in her future endeavors."
Thompson sent a letter to President Donald Trump a few weeks ago saying she would be leaving her job, but she is not officially departing until late October, according to a source who's close with her.
Thompson, who came directly into the Trump administration after more than 25 years in the Army, is looking forward to continuing her career in the private sector, the source close to her explained. The source also said the timing felt right for Thompson to leave, with enough time for the administration to find a replacement, noting that "it's delicate and hard to leave during an election year." The source denied that the Butina controversy was behind Thompson's departure.
Thompson will attend the United Nations General Assembly next week, the source said, where she will have a full schedule -- but it does not include any meetings with Russians.
There are concerns from officials within the Trump administration and from members of Congress about Thompson being the primary US interlocutor with the Russians.
Butina, who was convicted of crimes relating to promoting Russian interests during the 2016 election, attended Thompson's wedding, two sources told CNN. Thompson denies the two ever met. The June 2017 wedding was officiated by Paul Erickson, who at the time was dating Butina, according to two source familiar with the event. Erickson was a family friend of Thompson's parents for more than 20 years. Multiple sources said Butina attended the wedding with Erickson.
Thompson claims that she did not reveal her relationship with Erickson before her congressional confirmation hearing because of legitimate timing reasons: The Department of Justice did not reveal the criminal complaint into Erickson for his relationship with Butina until after Thompson was confirmed for her job in April 2018.
Thompson's version of the story seemed unbelievable to some, sources familiar with the case explained. Their disbelief lay in the fact that the first reputable news outlet to report the friendly relationship between Butina and Erickson was The New York Times in December 2017, which indicates Thompson must have known that there were looming questions about Erickson.
When Senate Foreign Relations ranking Democrat Bob Menendez of New Jersey wrote a letter over the summer asking Thompson a series of questions, she sought to defend herself.
Thompson wrote back that she "did not recall" ever meeting Butina, did not invite Butina to her wedding and did not know of Butina's connection to the Russian government until the Justice Department unsealed the criminal complaint in July 2018.
Officials on Trump's National Security Council who did not work well with Thompson were also quick to point out her ties to Butina. Some of the top NSC officials did not agree with her ideologically on arms control, sources explained.
Pompeo also did not want Thompson engaging directly with Russians, given this controversy, which made it hard for her to do her job, two sources said. The source close with Thompson pushed back on that characterization and said Thompson's work was never impacted by the Butina controversy.
Thompson will be leaving a pivotal post vacant at the State Department while the White House is conducting intense interagency talks to develop options for Trump to pursue a new nuclear pact. Given the lack of progress on this front, nuclear experts are worried that the administration could upend the New START Treaty, which expires in 2021, and leave it without a replacement.
CNN's Caroline Kelly contributed to this report.
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