The leaks are believed to be the most serious US security breach since more than 700,000 documents, videos and diplomatic cables appeared on the WikiLeaks website in 2010.
The leaked documents were believed to be the most serious US security breach since 2010.
"He's fit. He's strong. He's armed. He's trained. Just about everything you can expect out of some sort of crazy movie," said one person of the perpetrator
"If this document is accurate, it either shows Vucic's duplicity vis a vis Russia or he's under enormous pressure from Washington to deliver weapons to Ukraine," said Janusz Bugajski
US officials are trying to find the source of a leak of classified documents detailing a wide array of topics from Ukraine's air defenses to Israel's Mossad spy agency.
The leaked classified US documents purportedly reveal details of Ukrainian military vulnerabilities and information about allies including Israel, South Korea and Turkey.
Among the leaked Pentagon documents was one that outlined scenarios in which Israel may supply Ukraine with weapons.
The Russian embassy in Washington and the Kremlin did not respond to requests for comment.
The documents appear to have been altered to lower the number of casualties suffered by Russian forces, the US officials said.
The US officials spoke on condition of anonymity given the sensitivity of the matter and declined to discuss the documents in any detail.