The statement said that the secretary-general encourages all sides to engage, in good faith, in serious talks that would lead to a lasting solution to the political crisis and address the urgent economic and humanitarian needs of the Zimbabwean people.

"The secretary-general also urges the enabling of humanitarian operations in order to allow the provision of assistance to those in dire need," said the statement.

Speaking at the signing ceremony, President Mugabe said his party and the opposition had agreed to amend the country's constitution.

Mugabe also urged negotiations to be held free from influence and pressure from Europe and the United States, which are seeking new sanctions on Zimbabwe.

For his part, Tsvangirai promised that he would act to put the interests of Zimbabwe at the forefront.

Mbeki said the deal committed both sides to an intense process to try to complete substantive negotiations as quickly as possible, adding that all parties involved recognized the urgency to hold the negotiations, which is aimed at ending the political crisis facing the country.

Mugabe was declared winner of the June 27 presidential run-off by the Zimbabwe Electoral Commission, a result rejected by Tsvangirai, who received a leading number of votes in the first round of polls but failed to obtain an absolute majority.

Tsvangirai boycotted the run-off, citing various reasons, including political violence.

(Xinhua News Agency July 22, 2008)