North Korea today said it has received United Stats President Donald Trump's letter wishing a happy birthday to leader Kim Jong Un, but warned it would only return to nuclear talks if Washington fully accepts its demands.<br />'' <br />'' The US President and Kim have held three meetings since June 2018 but negotiations over denuclearisation have been largely deadlocked since the break-up of a summit in Hanoi last February.<br />'' <br />'' Official KCNA news agency said, North Korea's Foreign Ministry Adviser Kim Kye Gwan has said, in a statement, that it would be absent-mindedness to expect Pyongyang to resume dialogue because of that warm personal relationship.<br />'' <br />'' On the gridlocked nuclear talks, he said that reopening dialogue would only be possible in the case of Washington's absolute agreement on the issues raised by North Korea in previous talks. <br />''  <br />