The Director of U.S. National Intelligence James Clapper said on Tuesday that the U.S. policy of trying to persuade North Korea to denuclearize "is probably a lost cause" and the best that could probably be hoped for was some kind of cap on the country's nuclear capability.

"They are not going to do that - that is their ticket to survival," Clapper said when asked at the Council on Foreign Relations think tank whether he thought North Korea would give up its nuclear weapons.