Top officials from NATO and Russia have clashed in public over who is to blame for the dramatically worsened state of East-West relations.

NATO Secretary-General Jens Stoltenberg said Friday "the big difference is that we are a defensive alliance."

Speaking to a leading member of Russia's parliament, Stoltenberg told him, "you send troops into other countries."

The Russian, Konstantin Kosachev, flatly denied Russia is using its regular troops in Ukraine. Kosachev, chairman of the international affairs committee of Russia's State Duma, said the U.S.-led alliance talks about the need to respect international law and borders, but itself bombed a sovereign country, the former Yugoslavia, in 1999.

Stoltenberg and Kosachev spoke at a panel discussion organized by the Brussels Forum, an annual event sponsored by the German Marshall Fund.