SEOUL (AFP) - The United States and North Korea have agreed to hold two rounds of bilateral meetings before the North returns to multilateral nuclear disarmament talks, a US news report said.

The agreement was reached at last month's meetings in New York and San Diego between officials from the two sides, Foreign Policy magazine said on its website, in a report seen Wednesday.

The communist state, putting further pressure on the United States to start direct talks, announced Tuesday it has completed reprocessing spent fuel rods to produce more plutonium for its atomic weapons programme.

The US State Department responded that the plutonium production "runs counter" to the North's disarmament commitments and violates UN Security Council resolutions.

It said it has not decided when and where to hold bilateral talks involving the US special envoy to North Korea, Stephen Bosworth.

Foreign Policy, quoting an administration official, said "substantial progress" was made in talks between Sung Kim, the State Department's special envoy to six-party talks, and visiting North Korean official Ri Gun.

The North has said it is ready to return to the six-party nuclear disarmament talks which it abandoned in April, but only if it first has bilateral discussions with Washington to improve relations.

South Korea's chief nuclear negotiator Wi Sung-Lac told Yonhap news agency separately the United States is expected to decide soon whether and when to hold the bilateral dialogue.

Foreign Policy said Ri agreed that Bosworth would meet Kang Sok-Ju, first vice foreign minister, rather than chief nuclear negotiator Kim Kye-Gwan.

"Bosworth's visit would be seen as a failure unless some demonstrable progress was made and it is widely believed that only the top officials in Kim Jong-Il's regime have real negotiating authority," the magazine said.

Ri, however, "demurred" on Sung Kim's demand that the North abide by a September 2005 six-party nuclear deal, the magazine said.

This calls for North Korea's denuclearisation in return for economic aid, diplomatic recognition and the establishment of a permanent peace regime to replace the fragile armistice that ended the 1950-53 war.

The North wanted to resume talks "based on the idea of denuclearisation of the Korean peninsula, a nuanced but important distinction," the magazine said.

Pyongyang calls for the withdrawal of any US nuclear threat and a change in its "hostile" policy as a precondition for giving up its nuclear weapons.

The North quit the six-party talks in April after the United Nations censured its long-range rocket launch. It had vowed at the time to restart the nuclear programme which it shut down under six-party pacts.

It conducted an atomic weapons test in May, the second since 2006.