Editor's Note: The story was updated to include the most recent comment by U.S. President Donald Trump. "If it expires, it expires," U.S. President Donald Trump said in his interview with The New York Times when asked about his intentions to extend the New START treaty that officially ended on Feb. 5. The expiration would put an end to the last bilateral agreement limiting Russian and U.S. nuclear arsenals — a combined 80% of the world's total. Russia's President Vladimir Putin announced his