The UN's top humanitarian official arrived in the Saudi coastal city of Jeddah on Sunday for talks aiming for a ceasefire between Sudan's warring generals, a spokesperson said.
"Martin Griffiths is in Jeddah at the moment and the purpose of his visit is to engage in humanitarian issues related to Sudan," spokesperson Eri Kaneko said.
Fighting that broke out in Sudan on 15 April between army and paramilitary forces has killed at least 700 people, most of them civilians, wounded thousands and driven a mass exodus of Sudanese and foreign nationals.
A UN official said Griffiths would meet representatives of the two generals at the heart of the conflict, army chief Abdel Fattah Al-Burhan and Mohamed Hamdan Daglo, commonly known as "Hemedti", who heads the Rapid Support Forces.
There was no indication that Griffiths would play a direct role in discussions about a possible ceasefire.
Sudanese and Saudi officials have provided scant details about what the talks will cover and how long they will last.
A joint US-Saudi statement on Saturday described the meetings in Jeddah as "pre-negotiation talks".
Saudi Arabia has assumed a high-profile role in evacuations from Sudan, dispatching naval and commercial vessels to bring thousands of civilians across the Red Sea from the Sudanese coastal city of Port Sudan.
Riyadh's mobilisation on the humanitarian and diplomatic fronts reflects its desire "to be seen as a key regional interlocutor and player," said Hussein Ibish of the Arab Gulf States Institute in Washington.
"It can't effectively position itself to be a leading international force… if it doesn't at least try to broker in very destabilising nearby disputes," Ibish said.
"That said, it doesn't have to achieve success in any given field. It has to be seen as a key party involved in some or all of them."