Sudan's President Omar al-Bashir is pledging his government will not support rebels in neighboring South Sudan.
The Sudanese leader spoke Monday during a brief visit to the southern capital, Juba, where he met with South Sudan President Salva Kiir.
Bashir thanked Kiir for a "warm welcome" and went on to say Sudan will never support rebels against any neighboring government. He said that "would only cause instability, exhaustion of resources and destruction of ties between countries."
In the past, the two Sudans have accused each other of supporting rebels on the other's territory.
Meanwhile, substantive peace talks between delegates for Kiir and rebel leader Riek Machar appear finally set to begin in Ethiopia.
The sides negotiated for several days over the format and agenda of the talks. The chairman of the mediation team, Seyoum Mesfin, told reporters Monday the parties have agreed to discuss a proposed cease-fire, and the fate of pro-rebel officials detained by the government.
China is calling for an immediate end to hostilities in South Sudan, where three weeks of political and ethnic violence has killed more than 1,000 people and displaced about 200,000 from their homes.
Chinese companies have major investments in South Sudan's oil industry.
On Sunday, South Sudan Information Minister Michael Makuei says the government will not let the detainees go as part of the talks.
"We are not ready to negotiate on preconditions. This is why we are here. The question of the releases should not be annexed to the successful peace talks. We came here to talk peace without conditions and to come and tell us that 'release these people so that they talk' is a condition and we are not ready to accept any precondition," said Makuei.
U.S. Secretary of State John Kerry said Sunday his government will support those seeking peace, but will work for international pressure against those who use force to gain any advantage. Kerry said to reporters in Jerusalem, negotiations must be serious - not a "gimmick."
The talks in Ethiopia are being mediated by the East African regional bloc IGAD (Intergovernmental Authority on Development).
South Sudan's unrest began December 15 when renegade soldiers attacked an army headquarters. President Kiir accused Machar of a coup attempt. Machar has called for the army to overthrow the president.
Witnesses say some of the violence is ethnically motivated, with supporters of Kiir, a member of the Dinka tribe, and supporters of Machar, from the Nuer tribe, targeting each other.