Donald Trump has told Vladimir Putin he does not want to renew a 2010 arms control treaty that limits the number of strategic nuclear weapons the US and Russia can deploy. Trump angrily denounced the New Start Treaty in a 28 January phone call to the Russian leader. The phone call began with a friendly exchange, with both leaders stressing their own popularity and complimenting each other on their domestic support. Then when Putin brought up two issues on which their countries had cooperated on, New Start and the 2015 nuclear deal with Iran, Trump lost his temper, dismissing both as strategic losses for the US given away by Barack Obama.
https://www.theguardian.com/world/2017/feb/09/trump-putin-call-nuclear-deal-new-start-treaty
