Sudan and South Sudan agreed Monday during a visit to Juba by President Omar al-Bashir to consider setting up a joint force to protect vital oilfields, his foreign minister said.

"Sudan and South Sudan are in consultations about the deployment of a mixed force to protect the oilfields in the South," Ali Ahmed Karti said, adding that Juba had come up with the idea.

The proposed deployment would cover all oilfields, including those located along the border between the two countries, said Karti.

"At the request of the South Sudanese oil ministry, 900 oil experts from Khartoum will be sent to South Sudan to help the recovery of production" hit by the conflict, he added.

Bashir visited Juba as South Sudan's government and rebels were starting formal peace talks in Addis Ababa aimed at ending more than three weeks of unrest.

South Sudan won independence from Khartoum in 2011 after decades of war, but the north remains a key player -- serving as the export route for the South's oil.

On Sunday, the South's army spokesman Philip Aguer said government forces were on the offensive in the oil-producing Unity and Upper Nile states in the north of the country.

Despite its oil wealth, accounting for about 80 percent of 2012 gross domestic product, South Sudan is one of the continent's least developed countries.

Oil production in South Sudan has slumped by about 15 percent since the fighting erupted.

It began on December 15, pitting army units loyal to President Salva Kiir against a loose alliance of ethnic militia forces and mutinous army commanders nominally headed by Riek Machar, a former vice president who was sacked last July.

The young nation's two major oil-producing states are among the four areas most affected by the fighting.

Since the South's independence, tensions have been high at times between the two former civil war foes, whose forces even clashed in May last year over Sudan's main oilfield at Heglig.