The United Nations Security Council has delayed voting on a package of sanctions against Zimbabwe.
In a letter to the UN, the Zimbabwean government said any new sanctions risked starting a civil war in the country.
This is the first meeting between Zanu-PF and the opposition MDC since June's run-off poll, which President Robert Mugabe won unopposed after the MDC pulled out because of violence.
South Africa President Thabo Mbeki is leading mediation efforts.
But MDC leader Morgan Tsvangirai has issued a statement saying the talks do not amount to formal negotiations.
Mr Tsvangirai insisted that MDC representatives were merely setting out the conditions under which talks could take place.
He added that nothing could happen while Mr Mugabe's ruling Zanu-PF party "continued state-sanctioned violence and repressive legislation", which he said was "designed to silence the Zimbabwean people".
Mr Tsvangirai also demanded an expanded mediation team that included a permanent African Union envoy.
Meanwhile, talks between Zanu-PF party and the MDC are due to resume in South Africa on Friday.
On the first day of talks, the MDC set a series of pre-conditions for the opening of formal negotiations. They include the release of more than 1,500 political prisoners and an expanded mediation team.
Last week, Mr Mugabe accepted the need for negotiations but demanded that he must first be recognised as president by the opposition.