The leaders of Sudan and of its semi-autonomous southern region say they have reached a deal on the terms of a referendum on independence.
It was one of four issues at the heart of crisis talks between President Omar al-Bashir and Salva Kiir.
Officials said they had agreed on the proportion of votes and turnout needed for the referendum to be binding. One other issue remains unresolved.
The peace process between North and South has been looking shaky.
The two leaders fought each other during the country's two-decade long civil war and have been uneasy partners since a peace deal - which has been looking increasingly shaky - was signed in 2005.
Elections are due in April next year and in 2011 the South will vote in a referendum on possible independence.
Representatives of Mr Kiir's party, the former Southern rebels of the SPLM, and the ruling National Congress Party held a joint news conference to announce the new deal hammered out in Khartoum.
The AFP news agency quotes SPLM secretary general Pagan Amum as saying: "With this agreement we announce the end of the crisis between the two partners."
He said MPs who had been boycotting parliament for the past 45 days would start attending sessions within 24 hours.
Full details surrounding the terms of the 2011 referendum have not yet been released, as both leaders will take the deal to their parties first, reports the BBC's James Copnall in Khartoum.
But a senior official for the SPLM told the BBC that a 50% plus one vote would be needed for independence, as long as the turnout was high enough.
He said that the minimum figure had been set at between 55% and 60%, and would be announced shortly.
The two leaders also achieved agreement on a referendum for one small region, Abyei, and popular consultations for two others.
The remaining sticking point concerns a law on the role of the national security service - essentially revolving around how much power this controversial body should have, our correspondent says.
A committee will be set up to decide the issue, which is particularly important in the run-up to next April's elections.
The apparent agreement on so many of the obstacles to the peace process comes a week after Southern leaders were arrested as they tried to organise a banned demonstration, our correspondent adds.
That event, and a worsening climate between the two sides, suggested to many the situation was getting desperate - so this agreement, if it is respected, is a major breakthrough, he concludes.
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