United Nations Secretary-General Kofi Annan called on the Democratic People's Republic of Korea (DPRK)and other nations on Wednesday to ratify the Comprehensive Nuclear Test Ban Treaty (CTBT)to pave the way for its entry into force.

"Our world can ill afford to fail,or even to be unduly delayed,in achieving a comprehensive nuclear test ban,"Annan said in a message to a conference in Vienna on facilitating the entry into force of the CTBT.

Delay increases the risk that nuclear testing might resume and jeopardizes efforts to take further steps toward the goal of nuclear disarmament,he warned.

"I therefore call upon all states that have yet to sign or ratify the treaty to do so without delay,"he told the three-day meeting in the message,delivered by Antonio Maria Costa,director-general of the UN Office at Vienna.

"Given the latest developments,I particularly direct this callto the Democratic People's Republic of Korea,as well as to the other eleven states whose ratification is needed for the treaty toenter into force."

"No nuclear testing must be tolerated under any circumstances,"Annan stressed,while calling on all relevant states to maintain amoratorium on nuclear-weapon test explosions or any other nuclear explosions.

The DPRK withdrew from the Nuclear Non-Proliferation Treaty (NPT)at the beginning of the year and has since been reported to have said it would develop nuclear weapons and might carry out tests.

To date,168states have signed the CTBT and 104have ratified it,but it will enter into force only when all 44states,deemed to have nuclear potential,ratify it.Of the 44nations,12have yet to sign or ratify the treaty.

The CTBT was opened for signature seven years ago.Under the terms of the CTBT,a global verification regime to monitor compliance with the treaty must be operational at the time of entry into force.