The top U.S. negotiator in talks to rid North Korea of nuclear weapons said Tuesday that Pyongyang must agree to a verification of its disarmament activities and the deal must be put in writing. North Korea agreed last year to disable its nuclear reactor in exchange for aid. But negotiations have since stalled after the Stalinist state denied it agreed to allow inspectors to take samples from its nuclear complex to verify past nuclear activities. The United States and other negotiating partners, however, have said the disarmament-for-aid pact hinges on the ability to confirm that the North has fully disclosed the extent of its atomic programs. Full Story