"We cannot continue talking and talking and talking without concretely proceeding to the implementation stage," said South African President Kgalema Motlanthe at the latest round of Sadc-sponsored Zimbabwe talks.
Southern African leaders remained locked in marathon talks early on Tuesday in a fresh push to end Zimbabwe's political deadlock between President Robert Mugabe and rival Morgan Tsvangirai.
The 15-nation Southern African Development Community (Sadc) leaders are trying to salvage a power-sharing deal signed last September, after another round of mediated talks collapsed in Harare last week.
In his opening address, South African President Kgalema Motlanthe called for the summit to resolve the political stand-off, which has seen Zimbabwe plunge further into economic crisis amid a deadly cholera epidemic.
Motlanthe said questions were continuously raised about Zimbabwe in Africa, with the expectation that the country's leaders under Sadc's aegis would resolve the impasse.
"I trust that we will not fail them," he said.
Increasing international pressure
Mugabe faced increasing international pressure on Monday with fresh European Union sanctions on his rule, and calls from US Secretary of State Hillary Clinton for regional leaders to do more.
"Clinton is very focused on this issue. She's very concerned about it," spokesperson Robert Wood told reporters in Washington.
"Certainly the membership of Sadc can do more," Wood said of the Sadc bloc, which is chaired by heavyweight South Africa.
"We encourage South Africa to do as much as it can to try to put pressure on Mugabe to do the right thing. But to date, Mugabe hasn't seemed to have any interest whatsoever in bringing about an end to the crisis in this country," he said.
Earlier on Monday, police fired rubber bullets to break up a protest by several hundred people in Pretoria, witnesses said.
No arrests were made but seven people were taken to hospital for treatment.
Regional leaders see a unity government ? that leaves Mugabe as president and creates a new prime minister post for Tsvangirai ? as the best chance to end Zimbabwe's political and economic crises.
But the pact has floundered over which party will control top public posts, including the home affairs ministry, which oversees the police.
Mugabe to go at it alone
Earlier, Mugabe's deputy information minister sought to pile pressure on MDC leader Tsvangirai to accept a deal by saying the veteran president was ready to go it alone.
"This summit is the last summit that is going to discuss this issue of an inclusive government," deputy information minister Bright Matonga told South African public radio.
"If it does not work today, definitely when the president comes back here (Harare), he has to form a new government with or without Morgan Tsvangirai.
EU foreign ministers on Monday tightened sanctions on Mugabe's government in Zimbabwe, putting European companies on the banned list for the first time, amid growing frustration about human rights and political abuses.
The widened sanctions bring the number of people on the list to over 200.
March's first round presidential election, in which Tsvangirai placed first but did not win an outright majority, was followed by a brutal wave of political violence.
Tsvangirai pulled out of the run-off, citing violence against his supporters, leaving Mugabe to declare a one-sided victory in June.
Since then Zimbabwe has plunged deeper into crisis amid massive unemployment and crippling hyper-inflation, with half the population dependent on food aid.