Friday’s "disengagement", the biggest threat to the fragile partnership in the eight months since it was formed, was sparked by the renewed detention of Prime Minister Tsvangirai’s top aide Roy Bennett, who goes on trial for terrorism on Monday.
"Tsvangirai is trying to send a strong signal to the guarantors of the unity accord that there are serious problems within his partnership with Mugabe," said Siphamandla Zondi from the Institute of Global Dialogue.
"We may see a total withdrawal from government, but that is not imminent at this stage. I see this disengagement as a calculated move to get help from outside."
Tsvangirai, whose flexing of political muscle follows months of strain over unresolved disputes with Mugabe’s Zanu-PF, has faced criticism that his signing of the unity pact was a compromise after initially winning polls in 2008.
"The greatest concession made by Tsvangirai was to win an election and let Mugabe to be part of government, but he has not even honoured some GPA agreements," said International Crisis Group political analyst Sydney Masamvu.
Tsvangirai’s move was to show Mugabe that MDC will no longer be the only unity partner to make compromises which Mugabe has taken as sign of weakness, he added.
A high court order for Bennett’s release on Friday was unlikely to shift Tsvangirai’s new tough stance, the analysts said.
"Bennett’s arrest is the trigger regarding MDC’s decision but it’s not the ‘be it and end all’; there are other outstanding issues," said Masamvu.
Describing Bennett’s case as symptomatic of the troubles facing the government, Tsvangirai said he will not resume ties until all issues are resolved, including a crackdown on his supporters and disputes over key posts.
Analyst Dirk Kotze of the University of South Africa said Bennett’s reinstated bail was unlikely to see a turn-around.
"Bennett is not the cause of the trouble, he’s the symptom of the trouble," he said.
The move allowed Tsvangirai to say that he had stood up to Mugabe and was not to be seen as a puppet of the government, but the MDC leader will have to carefully consider his next move.
"This is a strategic decision so you can’t use it very often," Kotze said.
"The MDC needs to use this most effectively in order to negotiate, to bargain something. Because if they don’t do it – if they just keep out and keep silent also, and don’t engage the Zanu-PF – then they are going to lose the impact of this."
Despite the unresolved matters, the Tsvangirai and Mugabe partnership formed in February, nearly a year after the disputed polls, has set Zimbabwe on the path to economic stabilisation after years of crisis.
Cheryl Hendricks at the Institute of Security Studies said Mugabe’s Zanu-PF was unlikely to pull out of the unity government as they had too much to lose.
Both parties had worked with the unity agreement for months without pulling out despite complaints, she said.
"This is a political game, it’s like a chess game…. Basically Tsvangarai is now throwing the ball back Zanu-PF, saying it’s time to come to the party, I think this time Mugabe has no choice."