Mugabe also criticised Morgan Tsvangirai, the leader of the largest faction of Zimbabwe's main opposition party, the Movement for Democratic Change (MDC), in front of thousands of party activists.
He said Tsvangirai was a "puppet" of the UK and the US.
Mugabe lambasted the US and Britain, who have criticised his rule, saying they were the country’s "enemies".
He said: "There will never be regime change here ... Never."
The president, who has ruled Zimbabwe since 1980, alleged that the two nations and their allies had used sanctions to undermine Zimbabwe's economy.
The south-east African nation has inflation of more than 100,000 per cent, unemployment of more than 80 per cent and dire food and fuel shortages.
The elections are the biggest threat to Mugabe reign since he took power.
Makoni is expected to gain votes from disillusioned Zanu-PF members.
However, he could also take votes away from Tsvangirai's fractured opposition and give Mugabe the majority of the vote.
Mugabe needs at least 51 per cent of votes to avoid a presidential run off.