MDC faction leader Arthur Mutambara spoke of progress after talks broke up for the night
Talks on rescuing Zimbabwe's power-sharing deal have ended without result but will resume in the morning, key leaders have said.
President Robert Mugabe and opposition leader Morgan Tsvangirai spoke after the first day of talks mediated by ex-South African President Thabo Mbeki.
Mr Mbeki brokered the agreement to share power last month.
Mr Tsvangirai threatened to pull out of it after Mr Mugabe gave key ministries to his own supporters.
The US state department has accused Mr Mugabe of "overstepping the bounds of the agreement".
Also on Tuesday, Zimbabwe's parliament held its first working session under opposition control since the disputed elections earlier this year. MPs heckled each other at the opening.
While the power-sharing crisis continues, life for normal Zimbabweans remains a constant struggle, the BBC's Jonah Fisher reports from neighbouring South Africa.
Two million people are currently in need of food aid, with that figure set to increase to almost half the population over the next three months, our correspondent says.
"There was no conclusion to the discussions," Movement for Democratic Change (MDC) leader Mr Tsvangirai said, leaving the hotel in the Zimbabwean capital.
"We will continue tomorrow at 1030 [0830 GMT]."
Mr Mugabe concurred, adding: "Continuing tomorrow means we have covered some area."
Commenting on the situation, US state department spokesman Sean McCormack said Washington wished to see "the implementation of [the] original agreement get back on track".
"And, of course, any implementation solution has to be one that is acceptable to the MDC and Mr Tsvangirai."
The European Union earlier condemned Mr Mugabe's "unilateral decision" and ministers hinted that they could extend sanctions.
Mr Mugabe allocated the main ministries, including defence, home, foreign affairs, and justice, to his Zanu-PF party at the weekend.
Mr Tsvangirai wants all cabinet positions to be revisited in discussions with Mr Mbeki, but Zanu-PF says only one ministry - finance - is up for discussion.
According to the original deal - which allocates 15 ministries to Zanu-PF, 13 to the MDC and three to a smaller MDC faction - only Zanu-PF has a ministerial seat vacant.
Questions about Mbeki
Before the talks began, Mr Mbeki's spokesman said he was confident he would be able to rescue the deal, which he brokered just before stepping down as president in September.
Mbeki, who stepped down last month, is in Zimbabwe as a private citizen
"We are convinced that we should be able in the end, no matter how long it takes, to reach a conclusion," said Mukoni Ratshitanga.
This is Mr Mbeki's first direct intervention since he resigned as South Africa's head of state. Correspondents say it is not clear if he will still wield the same clout in the negotiations.
Richard Dowden, director of the UK's Royal African Society, says Mr Mugabe has "made a mockery of the agreement".
"I think what the MDC will do is appeal directly to [ANC leader Jacob] Zuma where they know they have someone more sympathetic to them than Mbeki," Mr Dowden told the BBC's Today programme.