Negotiators from six nations agreed Saturday on steps to verify North Korea's nuclear disarmament, opening the final phase in tortuous efforts to rid the North of nuclear weapons. The agreement, reached after three days of talks, requires North Korea to finish disabling its main nuclear facility by the end of October. Meanwhile the United States, China and the other three nations taking part would complete promised deliveries of fuel oil and other economic aid. Beyond that, the envoys agreed to a robust verification team of experts who will visit North Korean nuclear facilities, review its documents and interview its technical experts, said a press communique read out by China's envoy, Wu Dawei, at the end of the meeting. Some specifics of the verification remained to be worked out, but experts and diplomats from the six nations hoped to agree on those steps by early September, said US Assistant Secretary of State Christopher Hill.