UN Secretary-General Ban Ki-moon learned in advance of the decision of climate chief Yvo de Boer to resign "with regret," and "will now embark on identifying and recruiting" the new climate chief, a UN statement said Thursday.

"The secretary-general has taken note of the announcement by Mr. Yvo de Boer this morning of his decision to resign from his post as executive secretary of the UNFCCC (United Nations Framework Convention on Climate Change)," said the statement, issued here by Ban's spokesman.

De Boer, 55, announced Thursday that he would step down in July to pursue a career in the private sector, five months before more than 190 nations are due to reconvene in Mexico for another attempt to reach a binding worldwide accord on controlling greenhouse gases.

"Mr. de Boer informed the secretary-general in advance of his decision and the secretary-general, with regret, respected his decision," the statement said.

In the statement, Ban thanked de Boer for his "strong commitment and professional support to the UNFCCC negotiations, and for guiding the UNFCCC Secretariat since September 2006."

The UNFCCC, an offshoot of the 1992 Rio summit, gathers 194 nations in the search for combatting the causes of man-made climate change and easing its effects.

"Mr. de Boer's contribution during this crucial period encompassing the negotiations in Nairobi, Bali, Poznan, and in Copenhagen will be remembered, and difficult to replace," the statement said.

"The secretary-general will now embark on identifying and recruiting the new executive secretary," the statement said. "He will consult the Bureau of the UNFCCC Conference of the Parties in that process."

In a press conference Thursday at the UN Headquarters in New York, Janos Pasztor, director of the UNFCCC, said that the secretary-general has "started recruiting process."

"We don't know how long this will take," Pasztor said. " Certainly, it will take a few months."

Pasztor noted that the UNFCCC will ensure a "very rapid recruitment process to minimize any possible disturbance," particularly in time before the UNFCCC conference in Mexico later this year.