SEOUL, May 14 (Reuters) - North Korea is likely to soon make its long-delayed declaration of its nuclear activities, which could then lead to fresh talks on ending Pyongyang's atomic ambitions, a South Korean official said on Wednesday.

North Korea has agreed to cooperate fully on verifying its nuclear declaration, a U.S. official said on Tuesday as he displayed some of the 18,822 documents Pyongyang has given Washington a few days ago about its plutonium programme.

Secretive North Korea missed an end of 2007 deadline to provide a list of its atomic inventory to China, the host of six-way nuclear talks. South Korean officials have said they see the declaration coming in the next few days or weeks.

"If you do the math from the process of the North submitting a declaration to China in a few days and China circulating it, you get the expectation that the resumption of the six-way talks would be in early June," South Korean Foreign Ministry spokesman Moon Tae-young said.

The declaration has been held up partly because of the North's reluctance to answer U.S. suspicions that it transferred nuclear technology to other countries, notably Syria, and had a secret programme to enrich uranium for weapons.

If isolated North Korea makes the declaration, it would be removed from a U.S. terrorism blacklist and be allowed to better tap into international finance.

South Korea was sending its top envoy to the nuclear talks to Washington where he will meet early next week with U.S. officials and a visiting Japanese nuclear envoy, Moon said.

The declaration is part of a deal among the two Koreas, China, Japan, Russia and the United States, under which the North, which detonated an atomic device in October 2006, would abandon all its nuclear programmes in exchange for economic and diplomatic incentives.

According to people briefed on the talks, the declaration is expected to be split in two parts -- a disclosure of North Korea's plutonium-related activities on the one hand and its "acknowledgment" of U.S. concerns about its suspected uranium enrichment and proliferation activities on the other.

U.S. officials have said they believe North Korea produced about 50 kgs (110 lbs) of plutonium, which proliferation experts said is enough for about eight nuclear bombs. (Reporting by Jon Herskovitz and Jack Kim in Seoul and Arshad Mohammed in Washington; Editing by Sanjeev Miglani)

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