Seoul, Sep 4 (DPA) North Korea said Friday that it was entering the final testing phase of uranium enrichment, which could give it a second way to produce nuclear weapons.

It also said that it was reprocessing plutonium for atomic weapons from spent fuel rods, a process believed to have produced the fuel for its two nuclear tests.

'Experimental uranium enrichment has successfully been conducted and entered into the completion phase,' North Korea's official Korean Central News Agency said, quoting from a letter sent to the UN. 'Reprocessing of spent fuel rods is in its final phase and extracted plutonium is being weaponized.'

The letter was released after North Korea made a series of conciliatory gestures in April toward South Korea in a sign of a potential de-escalation with the Stalinist country after tensions over its nuclear and missile programmes escalated earlier in the year and garnered Pyongyang international condemnation.

Highly enriched uranium can be used to produce nuclear weapons, but the two nuclear tests that North Korea has conducted - one in 2006 and another in May - are believed to have been done with plutonium reprocessed from fuel rods from its one functioning, plutonium-producing nuclear reactor.

The UN Security Council imposed further sanctions on North Korea in June after the nuclear test and a series of missile launches. North Korea reacted to those sanctions with threats that it would proceed with uranium enrichment and additional production of

plutonium.

The US has suspected for years that impoverished North Korea was pursuing uranium enrichment for the purpose of building nuclear weapons. Independent inspections of its nuclear sites are, however, impossible after Pyongyang threw out international

inspectors in April.