BEIJING - Nuclear disarmament negotiators gathered to discuss an agreement on rules about monitoring North Korea's nuclear activities in Beijing on Wednesday as six-party talks entered their third day. North Korea partly disabled its Yongbyon nuclear facility this year in a disarmament-for-aid deal, but the talks have so far failed to agree on a protocol to check the North's declaration of nuclear activities and move disarmament forward.Negotiators returned comments on a draft text offered by China on Tuesday that outlined a way to verify nuclear information. The state China Daily newspaper, quoting South Korean negotiator Kim Sook, said all sides had agreed to ship all promised economic aid to North Korea by the end of March.