Zimbabwe Prime Minister Morgan Tsvangirai said Tuesday he won't renegotiate over a draft constitution despite demands by President Robert Mugabe for major amendments to the document.

Tsvangirai said he was ready to reconsider "one or two issues" but Mugabe's party had completely rewritten the draft. Mugabe's ZANU-PF party, in a shaky coalition with the former opposition, "totally rejected" the draft that had been agreed upon and signed by representatives from all parties, he said.

The deadlock over the constitution could only be broken by regional leaders who brokered the coalition after disputed and violent elections in 2008, Tsvangirai told reporters.

"I hope they will act," he said.

Under the terms of the coalition, a referendum on a reformed constitution must be held before fresh elections. Mugabe's party wants sweeping powers it has held since independence in 1980 restored in the draft constitution.

Tsvangirai said the draft should now be put to Zimbabwean voters in the referendum and he urged ZANU-PF: "If you don't agree, go out and campaign for a 'No' vote."

Tsvangirai's party, the Movement for Democratic Change, has called on its supporters to back the draft with a 'Yes' vote.

Mugabe's party insists the draft is now in the hands of the three leaders of the coalition, known as the "principals," to iron out their differences.

"I am one of the principals. The principals cannot renegotiate the document and do not have a veto on the constitution. Let the people be the final arbiters, certainly not me," Tsvangirai said.

Mugabe's party has also said the president can call elections with or without a new constitution.

Tsvangirai said such a move would be in breach of the coalition agreement crafted by leaders of the Southern African Development Community, the 15-nation economic and political bloc, and would be illegal under the existing constitution.

"I don't think SADC will allow that," Tsvangirai said.

It was now up to the regional bloc and the chief mediator on Zimbabwe, President Jacob Zuma of South Africa, to "unlock" the stalemate over democratic reforms in the constitution and press for the implementation of other reforms set down in the power-sharing agreement before elections can be held by mid-2013.

"It would be suicidal for us to take part in elections without the necessary reforms. If it collapses it would spell doom for the conduct of free and fair elections," he said.

Tsvangirai said reforms of the state media controlled by Mugabe loyalists lagged far short of targets in the coalition agreement which called for an end to hate speech and media bias. Tsvangirai charged that he and his party are still vilified by what he called "the propaganda mouthpieces of ZANU-PF" of the state-owned news media that have mass audiences.

He said in the 36-month life of the coalition he had never appeared as the prime minister on state television progams or discussions.

Tsvangirai is shown by the sole television broadcaster in news clips, but often with a derogatory slant, report media freedom groups.

Tsvangirai on Tuesday described media reform as "key if this country is to have some semblance of a free and fair election."

"We will not take part in anything other than a fair election," he said. "Anything else is a circus."