The White House has warned of “actively advancing” arms talks between Russia and North Korea after Vladimir Putin’s defence chief travelled to Pyongyang on a mission to secure ammunition for the invasion of Ukraine. Sergei Shoigu, Russia’s minister of defence, was last month dispatched on the diplomatic mission to secure artillery munitions and an agreement to deepen military co-operation. According to a US intelligence assessment made public by National Security Council spokesperson John Kirby on Wednesday, those talks have progressed to a new phase. After the visit, Putin, Russia’s president, and North Korea’s leader, Kim Jong Un, exchanged letters “pledging to increase bilateral co-operation”, Kirby said, and another group of Russian officials also travelled to Pyongyang for follow-on discussions about an arms deal.