Talks to resolve a standoff in Sudan's national coalition government adjourned on Thursday without agreement, prolonging the crisis threatening a fragile peace agreement that ended two decades of war.

The former southern rebel Sudan People's Liberation Movement (SPLM) suspended its work in government last week after months of stalemate on implementing key elements of the 2005 deal.

After 3-1/2 hours of talks, SPLM Chairman and First Vice President Salva Kiir left his first meeting with President Omar Hassan al-Bashir since the crisis began, with officials saying discussions would continue.

SPLM officials would not yet return to work, they said.

"There was agreement to complete discussions on the outstanding problems in the deal," presidential spokesman Mahjoub Fadul said after the meeting in Khartoum. He did not specify when the talks might resume.

SPLM Deputy Secretary-General Yasir Arman told Reuters Kiir and Bashir had discussed outstanding elements of the peace deal.

Those elements include redeployment of northern troops from southern oil fields, mapping the borders of the oil-rich Abyei region, demarcating the north-south boundary and the fate of hundreds of political prisoners being held in northern jails.

"The meeting was cordial, frank and smooth between the two leaders," he told Reuters.

"The ministers will go back to work when the chairman of the SPLM has finished his talks and instructs them to go."

Bashir granted one SPLM demand on Wednesday by announcing a reshuffle of SPLM ministers -- which make up a quarter of the cabinet -- after a three-month delay.

But SPLM officials said the reshuffle was announced prematurely and two presidential advisors had not been appointed as requested.

Fadul said the SPLM and Bashir's National Congress Party had agreed the ministers would be sworn in without giving a date.

But Arman said discussions on the reshuffle would follow talks on the stalled peace deal.

He added the SPLM was 100 percent united behind Kiir.

The SPLM's action also had the support of many southerners.

"The walkout must continue until the NCP demonstrates that it is willing to move forward in one or two more points," said the independent daily Khartoum Monitor in an editorial, under the headline "Bravo SPLM."

The conflict, Africa's longest, cost 2 million lives and more than 4 million people were driven from their homes.

While both sides have insisted they do not want a return to war, recent relations have been strained. Bashir met SPLM Vice-Chairman Riek Machar and a high-level team on Tuesday after making them wait for two days in Khartoum.

The SPLM and local media reported demonstrations throughout southern Sudanese towns in support of the SPLM move. The southern army spokesman said the protests were mostly peaceful.

But tension broke out after one protest between former northern-sponsored militia soldiers now in the southern army, and police in Bentiu, the capital of the south's main oil producing state he said, adding one policeman was killed.

The international community has remained largely quiet and privately worried by the SPLM walkout, the biggest challenge to the 2005 peace accord.

The SPLM has given Bashir's party until January 9, the third anniversary of the landmark peace deal, to show progress on outstanding issues.