South Sudan's two rival leaders have reportedly met face-to-face in Addis Ababa for the first time since mass violence broke out in December.

According to the Reuters news agency, President Salva Kiir and his former vice president, Riek Machar, shook hands after meeting in the Ethiopian capital on Friday.

The US ambassador to South Sudan said she doubted the two could immediately reach an accord.

The talks between Kiir and Machar were expected to last one day, the AP news agency reported.

"I don't believe that they will meet and reach an agreement straight away. But if they can agree on a broad-based process on how to resolve the conflict, end the fighting, that would be a step forward," Susan Page, the US ambassador to South Sudan, said during a radio call-in show.

"People want peace. People don't understand why the country should go into war just less than three years since independence."

The leaders' talks should include an outline for an inclusive transitional government, Borge Brende, Norwegian foreign minister, said in an interview.

Norway is involved in trying to find a diplomatic solution to South Sudan's conflict.

"Otherwise, there will be consequences that will follow. We will increase our pressure on the parties. Even tougher measures will follow in the coming weeks if there is no political will to solve the crisis," Brende said.

The US announced sanctions this week against two men involved in the fighting in South Sudan, one loyal to Kiir and one loyal to Machar.

The move appears to be a warning to the leaders that more far-reaching sanctions are being considered.

Michael Lueth, South Sudan information minister, said on Wednesday that his government's priority is to first stop the violence. Later talks could be held about a transitional charter, he said.

Brende said Norway will host a donor conference on May 20 to assist with humanitarian needs in South Sudan.

Source: Al Jazeera and agencies