Vladimir Putin said Thursday he does not rule out Russia sending arms to isolated North Korea in what Washington called an “incredibly concerning” statement that threatens instability on the divided Korean peninsula. On a trip to Vietnam following a state visit to Pyongyang where Russia and North Korea signed a mutual defense pact, Putin also warned South Korea not to arm Ukraine. The Russian president said prospects of Moscow providing weapons to North Korea are repercussions for the West arming Kyiv, which is battling against a Russian invasion now in its third year. “Those who send these [m…