President Robert Mugabe fired back at the top U.S. envoy for Africa on Friday, saying Zimbabwe "will never collapse" after she warned that the world should act urgently to keep it from deteriorating into further chaos.

Jendayi Frazer, the U.S. assistant secretary of state for African affairs, said Thursday that questions about how much longer Zimbabwe can withstand hunger, disease and political stalemate before disintegrating ignore that "there is a complete collapse right now."

Mugabe, who has led the country for 28 years, said "they think that the Africans are idiots."

"What African countries would have the courage to order a military intervention of Zimbabwe?" Mugabe asked Friday at his ZANU-PF party's annual convention in Bindura, 60 miles northeast of Harare, the capital.

Most neighboring countries including regional giant South Africa are opposed to military intervention in Zimbabwe, where a cholera epidemic has killed 1,123 people and the United Nations says half the population faces imminent starvation.

Mugabe's critics blame his policies for the ruin of the once-productive nation. Mugabe blames Western sanctions for the nation's economic meltdown, though the European Union and U.S. sanctions are targeted only at Mugabe and dozens of his clique with frozen bank accounts and travel bans.

Frazer was in southern Africa consulting with regional leaders Thursday about what can be done to help Zimbabwe. A day earlier, South African President Kgalema Motlanthe stressed that he believed a proposed unity government was the solution, and that it must be formed quickly.

"We think that the person who has ruined the country ... that he needs to step down," Frazer said. "We're watching Zimbabwe become a failed state. We need to act now, proactively, in Zimbabwe."

Foreign ministers for the five Nordic countries also called for the end of Mugabe's "misrule," saying in a statement Friday that Zimbabwe's authorities "alone bear the responsibility for the tragic situation" facing the country.

Mugabe said Friday that "the only persons with the power to remove Robert Gabriel Mugabe are the people of Zimbabwe."

Opposition leader Morgan Tsvangirai beat Mugabe in March presidential elections at which his party also ended the 28-year domination of Parliament by Mugabe's party. But officials results said Tsvangirai did not win outright, and he withdrew from a runoff because of state-sponsored violence.

To break the impasse over the presidential votes, Mugabe and Tsvangirai agreed to form a unity government three months ago but have been deadlocked since over how to share Cabinet posts.

Tsvangirai said Friday that he will ask his party, the Movement for Democratic Change, to halt negotiations unless political detainees are released or charged by Jan. 1.

He told a news conference in neighboring Botswana that more than 42 members of his opposition party and civil society have been abducted in the past two months. They include three journalists and their whereabouts remain unknown.

"The MDC can no longer sit at the same negotiating table with a party that is abducting our members and other innocent civilians and refusing to produce any of them before a court of law," Tsvangirai said.

Also Friday, the central bank unveiled a new 10 billion Zimbabwe dollar bank note, the largest in a range of bills introduced since August when it slashed ten zeros from the old currency in a hopeless effort to keep up with stratospheric inflation.