SEOUL - South Korean Foreign Minister Ban Ki-moon today said his nomination to be next secretary general of the United Nations was an honour, but came at a difficult time.

"This should be a moment of joy, but instead I stand here with a very heavy heart," Ban told reporters in Seoul soon after the Security Council formally nominated him to succeed Kofi Annan at the end of the year.

"Despite the concerted warning from the international community, North Korea has gone ahead with a nuclear test."

The 192-member UN General Assembly must give final approval to Ban's nomination, which usually follows within a week or two. That vote is expected to be positive.

Ban said if he was appointed secretary general, he would make the most of the mandate given by the UN charter to "contribute as much as I can to the resolution of all kinds of problems, including the North Korean nuclear issue, that may threaten international peace and security".