MOSCOW, Oct 21 (Reuters) - President Vladimir Putin on Thursday said the Western-backed military development of Ukraine posed a real threat to Russia and the U.S. secretary of defense had effectively paved the way for Kyiv to join NATO after a visit earlier this week.

"Formal membership (of Ukraine) in NATO may not take place, but military development of the territory is already under way," Putin said. "And this really poses a threat to Russia. We are aware of that."

NATO defence ministers agreed a new master plan on Thursday to defend against any potential Russian attack on multiple fronts.

U.S. Secretary Of Defence Lloyd Austin said on Tuesday Russia had no right to veto Ukraine's aspirations to join NATO. (Reporting by Vladimir Soldatkin; Writing by Alexander Marrow; Editing by Mark Trevelyan)