Mr Tsvangirai said it was "probably the darkest day of our lives" for his MDC party
Zimbabwean President Robert Mugabe and opposition leader Morgan Tsvangirai have failed in their latest attempt to form a unity government.
After 12 hours of talks, Mr Tsvangirai said it was "probably the darkest day of our lives" for his party.
The MDC remained committed to a power-sharing pact but only if it had control of home affairs and finance, he said.
Mr Mugabe said he intended talks with the MDC to continue ahead of a regional summit on Zimbabwe's crisis next week.
The BBC's Peter Biles in Johannesburg says Zimbabwe's parliament is due to re-open on Tuesday, but without an effective government, the country remains paralysed and the suffering of millions of Zimbabweans goes on.
Parliament must change the constitution to create the post of prime minister for Mr Tsvangirai before the power-sharing deal can take effect.
Mr Mugabe said Monday's Harare talks, which broke up at around midnight, "didn't go well".
He accused Mr Tsvangirai of presenting new conditions.
STATE OF ZIMBABWE
Five million people - almost half population - need food aid
Central bank introduced Z$100tr note, worth about US$30 (Ł20)
Unemployment more than 80%
More than 2,200 people have died in cholera outbreak
But negotiations would go on, he said, before next Monday's Southern African Development Community summit, set for either in South Africa or Botswana.
"We will continue with discussions here at home," the 84-year-old told reporters.
On the eve of the negotiations, both sides had depicted it as a make-or-break moment for the power-sharing agreement struck in September.
The Movement for Democratic Change (MDC) leader said: "Unfortunately, there's been no progress because the very same outstanding issues on the agenda... are the same issues that are creating this impasse.
"For us as the MDC this is probably the darkest day of our lives, for the whole nation is waiting."
South African President Kgalema Motlanthe, his predecessor Thabo Mbeki and Mozambican leader Armando Emilio Guebuza mediated at the talks.
Under the deal, Mr Tsvangirai is supposed to become prime minister while Mr Mugabe stays president.
Arthur Mutambara, the head of an MDC breakaway faction who is supposed to become deputy prime minister under the pact, also joined the meeting.
The deal first faltered after the MDC accused Mr Mugabe's Zanu-PF of trying to hive off the most powerful cabinet posts.
The MDC has also demanded an end to the abduction of opposition and human rights activists by state security agents.
The political deadlock has exacerbated the problems facing Zimbabweans, from a cholera epidemic and an economic meltdown to food shortages and the collapse of basic services such as health and education.
Mr Tsvangirai, who arrived back in Zimbabwe on Saturday after an absence of more than two months, gained the most votes in elections last March but not enough for outright victory.
He pulled out of a run-off in June against Mr Mugabe, citing a campaign of violence against opposition supporters.
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