Russia’s foreign policy chief on Friday blamed what he described as “aggressive” U.S. policies for growing global tensions, noting Washington’s reluctance to extend a key nuclear arms pact. Russia-U.S. relations have been at post-Cold War lows since Moscow’s 2014 annexation of Ukraine’s Crimea. Speaking at an annual news conference, Lavrov said that the U.S. has stonewalled Russia’s push for extending the New Start nuclear arms treaty that expires in 2021.