Sharp political differences are likely to prevent opposition parties from rallying behind one candidate in the next presidential elections.
This increases the chances of Robert Mugabe winning a fifth term.
Diplomatic sources said this week that there had been moves behind the scenes, particularly from the international donor community, to coax smaller political parties to support presidential candidate and Movement for Democratic Change – Tsvangirai (MDC-T) leader Morgan Tsvangirai, who will make a third attempt to unseat the Zanu-PF leader.
The push for other presidential aspirants to rally behind Tsvangirai hit a brick wall after Welshman Ncube's Movement for Democratic Change (MDC-N) refused to form a coalition, sources said.
Also complicating matters are reports that Zanu-PF is courting Simba Makoni of the Mavambo/Kusile/Dawn (MKD) movement to rejoin its ranks after he deserted the party in 2008.
Makoni has rejected suggestions that he may rejoin Zanu-PF and insists he will be standing again as the MKD candidate in the presidential race.
Ncube's spokesperson, Nhlanhla Dube, said Ncube's party has resolved to field its own leader instead of forging an electoral pact with Tsvangirai.
"For our party, there is no deal to be made," said Dube. "For us, it is about the ethos and character of Zimbabwe post-Mugabe and that begins with voting for change you can count on all the time and every time.
"For us, principle, truth, fairness and honesty are the pillars on which our party and its president, Ncube, are founded. For these reasons Ncube will contest for the Zimbabwe presidency."
Dube added that the overtures to rally behind Tsvangirai were surprising because "all along we have been told by Tsvangirai's people that our party will not achieve anything measurable".
"We are now suddenly bombarded with pleas to join hands with Tsvangirai and assist him to defeat Mugabe. It seems their focus is not to defeat Mugabe but, apparently, [achieve] victory for Tsvangirai."
MDC-T welcomes change
A spokesperson for MDC-T, Douglas Mwonzora, said the issue of a coalition against Mugabe had not been raised in his party but that it would welcome such moves.
"Zimbabwe is yearning for change. We would welcome any agent of change," he said.
Psychology Maziwisa, a Harare-based political analyst and Tsvangirai critic, said an opposition coalition that rallied behind Tsvangirai was very unlikely in the forthcoming polls.
"There are a number of issues, not least the plausible accusation that Tsvangirai has dictatorial attributes," Maziwisa said.
"But perhaps the most important has to do with MDC-T's record over the past four years, one of corruption, neglect and amoral behaviour.
"Nobody wants to be associated with that, least of all at election time."