JUBA, Sudan - Sudan's former southern rebels will rejoin the national government to work through a stalemate on implementing a 2005 peace deal which ended Africa's longest civil war, spokesman Samson Kwaje said on Wednesday.

The Sudan People's Liberation Movement (SPLM) last week froze participation in Sudan's coalition government complaining it was being sidelined and that key elements of a January 2005 peace deal were being ignored.

The statement that the SPLM would rejoin government came shortly after President Omar Hassan al-Bashir, following a three-month delay, approved a cabinet reshuffle of SPLM ministers. The SPLM has about a quarter of the seats in Bashir's cabinet.

"President (of south Sudan) Salva Kiir is going (to Khartoum) tomorrow and there he will make a statement ... swear in the new ministers and then they will start work," southern Information Minister Kwaje told Reuters.

But other senior SPLM officials said the formal decision on whether to return to government would be taken after a meeting between SPLM Chairman Salva Kiir and Bashir on Thursday.

"Until Salva is satisfied with the outcome of the meeting with Bashir ... the one who is going to decide about resuming work or not is Salva," said one senior SPLM official who declined to be named.

The officials said the ministers approved by Bashir were not the ones Kiir wanted and the president should have waited until he met Kiir to make an announcement.

The SPLM decision to withdraw from the coalition government formed by the 2005 peace agreement was seen as the biggest challenge to date to the landmark deal which ended Africa's longest civil conflict.

The SPLM called it a "wake-up call" for their former foes, the National Congress Party, to encourage them to move on and implement the deal.

"I think it will happen, they've learnt a good lesson," Kwaje said.

But other SPLM officials said Kiir would have the final veto on whether the SPLM ministers would return to work.

"Definitely they will go back to work ... but ultimately on the directives of the President (Kiir)," said Michael Makuei, the Minister for Legal Affairs and Constitutional Development.

Kwaje said the SPLM was rejoining the government to work through unresolved issues together, but added southern leaders still wanted to see progress by the third anniversary of the 2005 peace deal on Jan. 9.

Sudan's north-south war claimed 2 million lives and drove 4 million from their homes. It largely pitted Khartoum's Islamist government against mostly Christian animist rebels.

On Tuesday SPLM Deputy Secretary-General Yasir Arman and Deputy Chairman Riek Machar said outstanding problems included the redeployment of northern troops from southern oil fields, resolving the status of the oil-rich Abyei region and constitutional violations such as political prisoners and encroaching on press freedoms.

Arrived at after more than a week of intense dialogue within the SPLM political bureau, diplomatic sources said not all within the party were happy at the latest position.

"They had no exit strategy," said one diplomatic source in Khartoum. Many were worried that despite both sides declaring they did not want a return to war, the move could derail the fragile peace process.