N.Korea demands US security guarantee for nuclear talks-Carter Thu Apr 28, 2011 1:31am GMT * Carter:N.Korea seeks guarantees to abandon nuclear programme * Says absence of peace treaty from 1950-53 war a "tragedy" * Experts say statesmen may still meet N.Korean leader, son By Jeremy Laurence SEOUL, April 28 (Reuters) - Reclusive North Korea has refused to make major concessions in talks with ex-U.S. President Jimmy Carter, insisting Washington provide some kind of security guarantee in return for giving up its nuclear weapons programme, the former leader said in a blog. Carter and three other former state leaders -- known...