India, Nov. 11 -- MOSCOW - Alexander Darchiev, Russia's ambassador to the United States and a veteran career diplomat, passed away suddenly on Wednesday at the age of 66, according to an official announcement from the Russian Foreign Ministry.

The sudden loss sent ripples through diplomatic circles in Moscow and Washington. In a formal statement released on social media, the Foreign Ministry expressed profound sorrow over his death, describing Darchiev as an "outstanding diplomat, an experienced leader, a valued colleague and mentor," and a "professional of the highest order" who managed one of the most critical and high-tension portfolios in Russian foreign policy.

The ministry did not immediately release details regarding the specific...