Tsvangirai's Movement for Democratic Change (MDC) is worried that the current constitution, which has been amended 19 times since 1980, grants the president too much power. Mugabe, aged 87, promises to run again and keep his job.

Political analysts speculate that Mugabe's Zanu PF party fears holding elections during 2013, as scheduled, because the long-serving president may by then be too frail to campaign.

"We just have to have elections next year," Mugabe told a party conference this month.

According to a diplomatic cable from 2008 released by Wikileaks, the president is believed to have cancer. Reports say he regularly visits Singapore for "rejuvenation treatments." Mugabe and his aides dismiss the accounts and insist he is fit.

The process of writing a new constitution, which the MDC hopes will be more liberal and democratic, has been started often and stopped regularly, owing to various feuds.

A referendum on the new constitution that was supposed to have been held during November 2010 has been postponed several times.

The latest such delay followed a demand to end the process by Munyaradzi-Paul Mangwana, who represents Zanu PF in the Constitutional Parliamentary Select Committee (COPAC), which is drafting the fundamental document.

"The Zanu PF position (is) that the constitution we come up (with) should reflect the views of the people," said Mangwana in an interview, adding that "75 per cent of the contents in the draft constitution were foreign."

"The people said they do not want some points but the drafters have included that. They said they want the death penalty to remain but the drafters were not including that," Mangwana charged.

When the MDC joined Zanu PF in a fragile coalition in 2008, after elections Tsvangirai said included violence against his supporters and rigging in favour of Mugabe, part of the deal was that Zimbabwe would have a new constitution before general elections are held.

"From the onset, we rightly pointed that this process will either be flawed or would take forever if left in the hands of politicians," said Madock Chivasa, a spokesman for the National Constitutional Assembly (NCA), a coalition of civic organisations.

Chivasa would rather see civil society groups compose a text, using input from communities.

The last effort to hold a referendum on a constitution ended surprisingly in 2000, when a draft was rejected by voters, in what was seen as a blow to Mugabe. The NCA played a key role in garnering support for the "no" vote.

Despite losing that vote, Mugabe went ahead with controversial land reforms, which saw white farmers' agriculture plots seized without compensation. The move was widely viewed as one of the causes of the country's stunning economic decline in recent years.

Mugabe and Tsvangirai will likely meet to talk about the latest impasse, but given the animosity between the two, no one is sure they can find a solution. Meanwhile, Minister of Constitutional Affairs Eric Matinenga says he is at a loss to give a date for another referendum.

"When you have these impingements, it becomes anyone's guess," Matinenga said, referring to the stoppage of the process.

Commenting on the latest halting, Charles Mangongera, a political analyst, said Zanu PF had no genuine reason to push ahead with the constitution making process.

"This is just part of Zanu PF's desperate attempt to derail the process in order to force an early election under the constitution," said Mangongera.
Despite the flawed process and ongoing repression against MDC activists, the party says it will not pull out of the ruling coalition. The MDC sees itself as the rightful winner of the 2008 elections and, therefore, belonging in government.

"We know the aim is for us to pull out of the government. We will not. We would have betrayed our people, (since) we are the ones that won the last credible election," said Douglas Mwonzora, an MDC spokesman on constitutional issues.

"So, Zanu PF must try other tactics if it wants to frustrate us.”

By Special correspondent