Norway's ambassador to the United Nations has accused Secretary-General Ban Ki-moon in a confidential letter of weak leadership, lack of charisma and angry outbursts, the Oslo newspaper Aftenposten newspaper reported Wednesday. The newspaper published what it said was a letter to Norway's foreign ministry from Mona Juul. "At a time when the UN and multilateral solutions to global crises are more needed than ever, Ban and the UN are notable by their absence," the letter read. Juul and her husband Terje Roed-Larsen - now a UN special envoy - had key roles in secretly brokering the now-failed 1993 Oslo peace agreement between Israel and the Palestinian Liberation Organization. Juul wrote that Ban showed "weak handling" of international challenges. She said he was a "passive observer" to Myanmar's arrest of opposition leader and Nobel Peace Laureate Aung San Suu Kyi, and she blasted his slow reaction to the civil war in Sri Lanka. Norwegian Foreign Ministry spokeswoman Marte Lerberg Kopstad refused comment on the authenticity of the letter. She referred reporters to Foreign Minister Jonas Gahr Stoere's comment to Aftenposten that he had noted the matter, and that he saw Ban as "hard working" and a "good listener." Juul's Norwegian-language letter was published halfway through Ban's term as UN secretary-general. He is due on an official visit to Norway starting August 31. She continued: "In other crisis areas, such as Darfur, Somalia, Pakistan, Zimbabwe and not in the least the Congo, the secretary-general seems irresolute." "Ban routinely has angry outbursts that even levelheaded and experienced co-workers have trouble dealing with," the letter said. Juul added that the mood among Ban's staff is "very tense." A spokeswoman for Ban, Marie Okabe, said at UN headquarters in New York that his office would have no comment on the newspaper's report Wednesday. She said Ban's office was aware of the report but had not yet confirmed the authenticity of the letter. Okabe noted, however, that "preparations are still ongoing" for Ban's trip to Norway's Arctic polar ice rim between August 31 and September 2, which has not yet been formally announced. Asked by reporters whether Ban's trip might be canceled or affected in any way because of the letter's criticisms, Okabe declined to speculate but did not rule anything out. The trip to various scientific research stations and retreating glaciers is intended to draw attention to the earth's warming as the UN prepares for a climate summit in September and tries to build momentum for a new global climate treaty in Copenhagen in December. South Korean Ban became UN leader in January 2007. Roed-Larsen is his special envoy for implementation of a 2004 Security Council resolution on Syria and Lebanon.