The letter to the International Atomic Energy Agency noted "that a working-level delegation of the IAEA has been invited to visit (North Korea) as it is confirmed that the process of de-freezing the funds of (North Korea) at the Banco Delta Asia in Macau has reached its final phase," the North's Korean Central News Agency reported.

The inspectors were invited for "discussions of the procedures of the IAEA's verification and monitoring of" shutting down its Yongbyon reactor, the report said.

North Korea had refused to act on its February pledge to disarm until it got access to $25 million once frozen in a US-blacklisted Macau bank. The US accused Banco Delta Asia of helping North Korea's government pass fake $100 bills and launder money from weapons sales.

Claiming the financial freeze was a sign of Washington's hostility, North Korea boycotted international nuclear talks for more than a year, during which it conducted its first-ever atomic bomb test in October.

In an attempt to win North Korea's promise to start dismantling its nuclear program, the US agreed earlier this year to give its blessing for the money to be freed.

The US, Japan, China, Russia and the two Koreas took part in the arms negotiations that prompted the February pledge from the North to stop making nuclear weapons in exchange for aid and political concessions.