Zimbabwe's main opposition leader has said he will not join forces with an ex-minister who last week said he would challenge President Robert Mugabe.
Mr Tsvangirai said he was confident of victory
Morgan Tsvangirai dismissed former finance minister Simba Makoni as "old wine in a new bottle".
Mr Makoni is seen as a reformer but Mr Tsvangirai said he shared the blame for Zimbabwe's economic crisis.
Both men say they will contest next month's poll, along with a candidate from another opposition faction.
"Dr Makoni has been part of the establishment for the last 30 years and has witnessed our country deteriorate to this unprecedented level. He is equally accountable as Robert Mugabe for the omissions of Zanu-PF," Mr Tsvangirai said.
"I believe that what Dr Makoni is trying is to reform an institutionalised dictatorship. That is not my agenda."
Mr Makoni was expelled from the ruling party last week after saying he would stand against Mr Mugabe on 29 March.
1980: Named deputy minister aged 30
2002: Sacked as finance minister after argument with Mugabe
2002: Went to South Africa
Possible support of Zanu-PF heavyweight Solomon Mujuru
There had been speculation that Mr Tsvangirai could stand aside to let Mr Makoni be the main anti-Mugabe challenger.
There are also reports that Arthur Mutambara, from the other faction of the Movement for Democratic Change, could join forces with Mr Makoni.
Mr Tsvangirai said he was confident of victory but accused Mr Mugabe of planning electoral fraud.
"Mugabe may rig it, may steal it, but we would have won it... I have no doubt in my mind, we will win it," he said.
The MDC had insisted on a new constitution before the elections, as well as guarantees they would be free and fair.
Previous polls have been characterised by violence and allegations of fraud.
Zimbabwe has the world's highest annual rate of inflation - 26,000% - and only an estimated one adult in five has a job.
Mr Mugabe's critics blame the economic crisis on his policies, especially the seizure of white-owned farms.
He blames a western plot to bring him down.