Sri Lanka's Government and Tamil Tiger rebels have agreed to share power in a federal system, to end 19 years of civil war on the island.

The joint declaration came at the end of four days of peace talks in the Norwegian capital, Oslo.

Both parties have made an unprecedented historic decision - our struggle was based on the concept of self-determination

Rebel negotiator Anton Balasingham

The Norwegian Government, which is mediating in the talks, said the two sides had agreed on "internal self-determination based on a federal model within a united Sri Lanka".

Under Thursday's deal, minority Tamils would have autonomy in the largely Tamil-speaking north and east of the island.

Chief government negotiator GL Peiris said the agreement was "irreversible". "It is a commitment to peace," he said. "There is not going to be war."

Anton Balasingham, the chief rebel negotiator, described developments as historic.

Security forces may be united

Both sides have come closer to a possible political solution after the Tamil Tiger leader Velupillai Prabhakaran said last week he would settle for less than outright secession.

Meanwhile, Japan has agreed to host an international aid donors conference next May or June to raise vital funds with which to rebuild Sri Lanka's war-devastated areas.

Constitution

Despite doubts about the handling of the peace process, the opposition party of President Chandrika Kumaratunga welcomed Thursday's deal, too.

A senior presidential aide said the party supported devolution within a federal framework - the president herself had recommended it in the past.

At the moment we have no interest in dissolving parliament

Anura Bandarinaike, presidential adviser

Neither government nor rebels had expected to get as far as agreeing on such a core political issue at this stage, the BBC's Lars Bevanger in Oslo says.

But he adds that parliament must approve any change to the constitution, requiring a two-thirds majority the government does not have.

It must also deal with a quirk in the constitution which allows the president to dissolve parliament a year into its term.

That anniversary was reached on Thursday.

The president's supporters, however, say early elections are a "last resort".

"At the moment we have no interest in dissolving parliament," Anura Bandaranaike, her brother and chief adviser, told reporters.

Rebuilding

Why should we believe them this time? - I lost everything

Tamil refugee

More than 60,000 people were killed in Sri Lanka between 1983, when war began, and the signing of a ceasefire in February this year.

People yearn for peace, and for the island's shattered economy and infrastructure to be rebuilt.

Shariya Wanigasekara, a teacher from the Sinhalese community, says the whole atmosphere has changed because of the peace process.

"It is a feeling of security away from the fear of bombs exploding everywhere," he told the Associated Press.

Neelan Sathyaseelan, a Tamil forced to flee his home, was more sceptical whether the government could ensure lasting peace.

"Why should we believe them this time? I lost everything. My land is now full of mines," he said.