A summit of 14 southern African nations has agreed that South African President Thabo Mbeki should try to mediate in the political crisis in Zimbabwe.
Zimbabwe police raided opposition headquarters on Wednesday
Mr Mbeki will aim to formally arrange talks between Zimbabwean President Robert Mugabe and the opposition.
The meeting also called on the West to drop sanctions and appealed to Britain to "honour its commitments" to fund land reforms in its former colony.
The Tanzania summit came amid rising concern about the Zimbabwe crisis.
Political violence is increasing in the country, which is beset by unemployment and poverty, and suffers the world's highest inflation - 1,700% a year.
Back from brink
Diplomats said before the summit that the leaders would tell President Mugabe that he should not stand for re-election next year, but there has been no word on whether they did so during their closed-door meeting.
The decision had been taken to promote dialogue, Tanzanian President Jakaya Kikwete said at the end of the summit of the Southern African Development Community (SADC).
"Of course the appeal to parties is to be co-operative and give this initiative a chance, also for the parties to exercise restraint and avoid anything that's going to inflame the situation," Mr Kikweti told a news conference.
The summit, which was attended by Mr Mbeki and Mr Mugabe, echoed the demands of the Zimbabwean government for all sanctions against the country to be lifted.
Britain and other Western countries have imposed targeted sanctions, including a travel ban on Mr Mugabe and his circle.
The meeting's outcome will probably disappoint the opposition, which had hoped for a much tougher line, says the BBC's Peter Greste in Dar es Salaam.
Their resolution also falls far short of the action urged by the US, which had called on the SADC summit to hold Mr Mugabe to account "for his misrule, not only over the last few weeks but over the last few years".
Amid the rising tension, Zimbabwean police on Wednesday cracked down further on the opposition.
The Movement for Democratic Change (MDC) said leader Morgan Tsvangirai was held for several hours after Wednesday's police raid on the party's headquarters in Harare.
Police denied he was among those arrested.
The policy-making body of Mr Mugabe's Zanu-PF is due to meet on Friday to decide whether to postpone the elections and, if not, who its candidate will be.
Speaking to the BBC as the summit got under way, Mr Mugabe's spokesman, George Charamba, said the president would stay for as long as he had the popular vote.
The pressure for change, he said, was coming from the US and Europe, and Zimbabwe was hoping for the support of other African nations.
"Our expectations are very, very simple: to recognise that Zimbabwe is under assault... it is under assault from Western countries that have imposed illegal sanctions on it," Mr Charamba said.
Mr Mugabe, who has governed Zimbabwe since its independence in 1980, has blamed the opposition for the recent violence, accusing it of staging attacks.
He has also dismissed complaints from the West about human rights abuses and political oppression as the whining of old colonists.
The SADC summit also discussed the violence in DR Congo.