Ban, 66, a former South Korean foreign minister, already had assurances of support from the United States and other key members of the U.N. Security Council, diplomats said in March.

Ban's first term ends on December 31. He is unopposed for re-election so far.

"As I approach the end of my term of office as the secretary-general of the United Nations, I am humbly submitting my name for the consideration of the members of the Security Council for a second term," said Ban's letter to Gabon's U.N. ambassador, Nelson Messone, this month's council president.

He sent a similar request for support to the 192-nation General Assembly.

In the letter to Messone, Ban said he and the 15-nation council had "found common ground on critical global issues of peace and security -- from Somalia to Sudan, Cote d'Ivoire (Ivory Coast) to Afghanistan, Iraq and the Middle East and far beyond."

"I am proud of all we have done together, even as I am mindful of the formidable challenges ahead," he wrote.

Reuters