Zimbabwe's principal political protagonists, Robert Mugabe and Morgan Tsvangirai, have signed an agreement which establishes a framework for substantive negotiations to end the country's political crisis.

South African foreign affairs spokesman, Ronnie Mamoepa, confirmed this in a statement issued from Harare Monday.

"The agreement was signed by President Robert Mugabe, Morgan Tsvangirai and [opposition leader] Arthur Mutambara," Mamoepa said.

South Africa's President Thabo Mbeki, the Southern African Development Community (SADC) facilitator of talks, flew to Harare on Monday morning for the signing ceremony.

Mamoepa described the "Memorandum of Understanding" signed by the three leaders as "a positive step forward in the ongoing dialogue among the parties."

The impetus for the final breakthrough in the "talks about talks" which have been conducted over recent weeks appears to have been a decision on Friday to set up a "reference group," comprising African Union, United Nations and SADC diplomats with whom Mbeki will liaise. Zimbabwe's Movement for Democratic Change has repeatedly challenged Mbeki's impartiality.