"I still hope that conditions can be created for the DPRK (Democratic People's Republic of Korea) to return to the Non-Proliferation Treaty at the earliest possible date," International Atomic Energy Agency chief Mohamed ElBaradei said here.

Addressing the IAEA's general conference which opened here Monday, the watchdog chief said that North Korea had asked agency inspectors last week to remove seals and surveillance equipment from the reprocessing plant at Yongbyon.

"They also informed the inspectors that they planned to introduce nuclear material to the reprocessing plant in one week's time -- that means this week -- and that the inspectors would have no further access to the reprocessing plant," ElBaradei told delegates.

The IAEA chief had already revealed last week that North Korea was preparing to restart a nuclear reprocessing plant used to make weapons-grade material as a crucial six-party disarmament-for-aid deal foundered.

Under the six-country pact announced in February 2007, North Korea agreed to disable and dismantle key nuclear facilities and allow UN atomic inspectors to return in lieu of one million tonnes of fuel aid and its removal from a US list of terrorist states.

But North Korea announced last month it had halted the process in protest at Washington's refusal to drop it from the US blacklist of countries supporting terrorism, as had been promised.