Zimbabwe is on a razor's edge and South Africa, Britain and the United States need to act to help end President Robert Mugabe's "suicidal reign", opposition leader Morgan Tsvangirai said on Monday.

No results from the country's presidential election nine days ago have been released and Tsvangirai's Movement for Democratic Change has asked Zimbabwe's High Court to force their release.

"Our country is on a razor's edge," Tsvangirai wrote in Britain's Guardian newspaper on Monday. He said the MDC's victory in parliamentary elections had been replicated in the presidential vote and called for international pressure. "This is also the time for firm diplomacy. Major powers here, such as South Africa, the U.S. and Britain, must act to remove the white-knuckle grip of Mugabe's suicidal reign and oblige him and his minions to retire," Tsvangirai said.

He also urged the International Monetary Fund to withhold one billion pounds ($2 billion) in aid unless Mugabe accepts the poll results and hands over power.

"Adept at stealing elections from the hands of voters, Mugabe is now amassing government troops; blocking court proceedings where we have attempted to seek an order simply for the electoral commission to release the final tally of the March 29 poll; raiding the offices of the MDC and casting a pall of suppression and gloom over the country," Tsvangirai said.

Zimbabwean High Court judge Tendai Uchena adjourned until later on Monday a hearing into the MDC's application to consider an electoral commission argument that he did not have jurisdiction. Mugabe suffered his first election defeat when ZANU-PF lost control of parliament in the March 29 elections.

ZANU-PF and independent monitors' projections show Tsvangirai has won the presidential election but will be forced into a runoff vote after failing to win an absolute majority. The ruling party's strategy to stay in power includes legal challenges to some of the parliamentary results and the mobilisation of pro-government militias before any runoff.