U.N. spokesman Stephane Dujarric said Secretary-General Antonio Guterres spoke to Kohler and expressed deep regret at the resignation, "but said he fully understood the decision and extended his best wishes to the personal envoy."
Dujarric gave no details on the health situation of Kohler, 76. A politician from Germany's center-right Christian Democratic Union, Kohler served as president of Germany from 2004 to 2010. Guterres appointed him in August 2017 to the difficult job of trying to resolve the decades-long dispute between Morocco and the Polisario Front independence movement over the mineral-rich Western Sahara.
Last year, the U.N. Security Council called for accelerated efforts to reach a solution to the 43-year dispute over the territory. Morocco annexed Western Sahara, a former Spanish colony, in 1975 and fought the Polisario Front for 16 years. The U.N. brokered a cease-fire in 1991 and established a peacekeeping mission to monitor it and help prepare a referendum on the territory's future that has never taken place.
Morocco has proposed wide-ranging autonomy for Western Sahara, while the Polisario Front insists the local population, which it estimates at 350,000 to 500,000, has the right to a referendum. Kohler was able to get representatives of Morocco, the Polisario Front and the neighboring nations of Algeria and Mauritania around the same table in early December 2018 for the first time in six years, and though no significant progress was reported the parties remain committed to the U.N.-brokered talks that have strong Security Council backing.
At a second meeting in late March, the parties also failed to make headway on the key issue of how to provide for "self-determination." Kohler cautioned that "many positions are still fundamentally diverging" and that nobody should expect "a quick outcome."
He said at the time that he planned to host another meeting. Dujarric, the U.N. spokesman, said the secretary-general "expressed his profound gratitude to Mr. Kohler for his steadfast and intensive efforts which laid the foundation for the new momentum in the political process on the question of Western Sahara."
"The secretary-general is also grateful to the parties and the neighboring states for their engagement with Mr. Kohler in the political process," Dujarric said.