The Democratic Republic of Congo's president, Joseph Kabila, is in Harare for talks aimed at saving Zimbabwe's fragile unity government.
Mr. Kabila is expected to begin talks Monday with Zimbabwe's President Robert Mugabe and Prime Minister Morgan Tsvangirai.
Mr. Tsvangirai and his MDC party suspended cooperation with Mr. Mugabe and his ZANU-PF party on October 16. The MDC says ZANU-PF is trying to undermine last year's power-sharing deal with a campaign of arrests and assaults against MDC officials.
Mr. Kabila is visiting Harare in his capacity as chairman of the Southern African Development Community, or SADC.
Officials said Monday that three southern African leaders will hold a summit Thursday in hopes of resolving the Zimbabwean crisis.
A Tsvangirai spokesman said Mozambique's President Armando Guebuza, Swaziland's King Mswati, and Zambian President Rupiah Banda will hold talks in Mozambique's capital, Maputo.
Last week, a SADC delegation recommended that an urgent regional summit on Zimbabwe be held as soon as possible.
SADC chairman Mr. Kabila has said the power-sharing deal is still binding and is the only way forward for Zimbabwe.
The unity government was set up in February, nine months after the end of disputed elections marred by violence against MDC supporters.
The government is trying to pull Zimbabwe out of a long economic crisis marked by years of hyper-inflation and shortages of food and fuel.
Some information for this report was provided by AP and Reuters.