The African Union on Tuesday rejected tougher action against Zimbabwe saying only dialogue could solve the deepening crisis, while US President George Bush joined calls for President Robert Mugabe to step down.
Zimbabwe's government, which accuses Western powers of exploiting a cholera epidemic that has killed nearly 600 to bring Mugabe down, said it was taking serious measures to deal with the threats.
"It is time for Robert Mugabe to go," Bush said in Washington.
"Across the continent, African voices are speaking out to say now is the time for him to step down."
But the AU made clear it did not back calls for much tougher action.
"Only dialogue between the Zimbabwean parties, supported by the AU and other regional actors, can restore peace and stability to that country," said Salva Rweyemamu, spokesperson for AU chairperson and Tanzanian president Jakaya Kikwete.
Rweyemamu said sending peacekeeping troops or removing Mugabe by force, as proposed by prominent figures including Kenyan Prime Minister Raila Odinga and Nobel peace laureate Archbishop Desmond Tutu, were not options.
"We have a serious humanitarian crisis in Zimbabwe. We have cholera. Do they think that we can eradicate cholera with guns?"
Many African leaders see Mugabe as a hero of the liberation war from white minority rule. They also resent foreign interference.
A senior government official said South Africa would oppose any move to send troops to Zimbabwe.
Mugabe and opposition leader Morgan Tsvangirai reached a power-sharing deal brokered by former president Thabo Mbeki in September. But they are deadlocked over how to implement it.
The spreading cholera, coupled with chronic food shortages, has highlighted the economic collapse of Zimbabwe, once relatively prosperous. Basic foodstuffs are running out and prices of goods are beyond the reach of many.
Zimbabwe ordered goods and service price cuts to December 3 levels after they surged when the central bank raised withdrawal limits.
Mugabe's spokesperson George Charamba said the West was using the cholera outbreak to bring down Mugabe, 84.
He accused Britain and the United States of trying to put Zimbabwe back on the UN Security Council agenda.
Information Minister Sikhanyiso Ndlovu said that country was taking measures to address any threats.
"I will not tell you what, but the government is taking serious measures to offset any threats and any further sanctions on the people.
"We won this country through the barrel of the gun and we will defend it the way we won it," he said.
In a sign that Mugabe's traditional ally China may be distancing itself, Beijing stressed the need for the formation of a unity government.
In an address at The Hague, former UN secretary-general Kofi Annan said: "Due to the abject failure of its leadership, Zimbabwe is now moving rapidly to becoming a full-blown failed state."
The UN Office for the Coordination of Humanitarian Affairs said the number of cholera cases stood at 13 960, with 589 deaths. "It is total chaos, three hospitals in Harare are closed due to a lack of personnel," spokesperson Elisabeth Byrs said.
The World Health Organisation (WHO) said up to 60 000 could catch cholera if the epidemic gets out of control.