United States Ambassador to the Russian Federation, John Sullivan, is leaving his position, the U.S. Embassy in Russia said Sunday.

Sullivan is exiting after nearly three years, having been appointed by then-President Donald Trump in 2019.

"Following his departure, he will retire from a career in public service that has spanned four decades and five U.S. presidents, including service as the Deputy Secretary of State and in senior positions at the Departments of Justice, Defense, and Commerce," the embassy said in an announcement.

Sullivan's exit comes seven months after a Russian invasion of Ukraine sparked a grueling war between the two countries. At the same time, Russian-American relations have been tense, with the U.S. imposing sanctions on Russia and military aid to Ukraine.

PUTIN TO ATTEND WAR GAMES WITH CHINA AND OTHER ALLIED NATIONS, EXPERT WARNS OF ‘DANGEROUS’ TIME

As it faces the effects of those sanctions, Russia has been increasingly cooperating with other American adversaries, Iran and China. Russia and China are currently in the middle of a week of war games together, which will include Russian and Chinese navies practicing "joint action to protect sea communications, areas or marine economic activity and support for ground troops in littoral areas," the Russian Defense Ministry said.

Iran recently sent Russia hundreds of drones to use against Ukraine, although Russia reportedly has been experiencing technical difficulties with them

PUTIN TO ATTEND WAR GAMES WITH CHINA AND OTHER ALLIED NATIONS, EXPERT WARNS OF ‘DANGEROUS’ TIME

Until there is a permanent successor in place, the embassy said the Charge d’Affaires at U.S. Embassy Moscow will be Elizabeth Rood, who has been Deputy Chief of Mission at the embassy since June.

In one of his last acts in office, Sullivan attended a farewell ceremony in Moscow for former Soviet President Mikhail Gorbachev, who died Tuesday.

The Associated Press contributed to this report.