"Everybody has to accept that if they want to dialogue. If they agree on that, and we are satisfied, then we shall go into dialogue and listen to them by way of ideas, but those votes can never be thrown away."
Latest death toll
The presidential run-off, boycotted by Tsvangirai after deadly attacks on his supporters, was widely denounced as a sham by Western governments.
On Friday, the MDC rejected Mugabe's demands an "unrealistic precondition".
The opposition also announced that 103 of its supporters - up from the previous 86 - have been killed and 1,500 arrested in a crackdown by Mugabe's supporters.
Those arrested included 20 legislators or parliamentary candidates, the MDC said in a statement, adding that 5,000 supporters - including polling agents and candidates for local councils - were missing.
| Mbeki, left, has been criticised for his apparent refusal to denounce Mugabe [AFP]
Mugabe escaped serious censure from his peers at this week's summit, which instead ended with calls for the formation of a national unity government.
But Botswana on Friday urged its neighbours not to recognise Mugabe's re-election and reiterated calls for Zimbabwe to be suspended from SADC, a regional bloc of 14 southern Africa nations.
"As a country that practices democracy and the rule of law, Botswana does not ... recognise the outcome of the presidential run-off election, and would expect other SADC member states to do the same," Phandu Sekelemani, the foreign minister, said.
Sekelemani said violence ahead of the June 27 run-off election "was not conducive to the holding of a free and fair election", adding that unrest "resulted in the loss of lives, destruction of property and displacement of people from their homes".
Nigeria has urged caution over calls for a unity government, saying such an idea should no become a "bail-out" or "rescue apparatus" for governments that have been rejected by the people.
"We are not opposed to government of national unity but we have to be careful here and not regard [the] Kenyan model [as] a one-size-fits-all arrangement," Ojo Maduekwe, Nigeria's foreign minister, said.
Independent observers say that although Botswana's has called for the Mugabe regime to be suspended from the AU and the SADC, chances of the region taking a hard line are slim with his biggest critic, Zambian President Levy Mwanawasa, fighting for his life.
Thabo Mbeki, the South African president and SADC's chief mediator on the crisis, has been fiercely criticised by the MDC over his consistent refusal to publicly denounce his Zimbabwean counterpart.
Mugabe said "we are happy that Mbeki continues to be the facilitator", adding "he has done nothing wrong".
The European Union (EU) has called for fresh elections in Zimbabwe, saying the goal of any solution to the crisis "must be to reconsult the Zimbabwean people on a free, democratic and transparent basis as quickly as possible".
"Only this can provide a long-term response to the serious difficulties currently being faced in Zimbabwe, which are threatening regional stability," a statement released on Friday said.
Calling "an immediate end to all forms of violence," the EU said that it "cannot accept the fait accompli of the outcome of the vote of 27 June," which returned the 84-year-old leader to office.