CAIRO (Reuters) -Egypt launched an attempt to mediate between Sudan's warring factions on Thursday at a regional summit, the latest in a series of international efforts to prevent a prolonged civil war and the deepening of a humanitarian crisis.

Fighting between Sudan's army and paramilitary Rapid Support Forces broke out in the capital Khartoum in April, and has spread westward to the fragile Darfur and Kordofan regions.

More than 1,000 civilians have been killed and 3 million people have been displaced, including 700,000 to neighbouring countries, according to the United Nations, which warns of a growing hunger crisis.

The United States and Saudi Arabia had negotiated a series of ceasefires, but suspended talks after violations. Earlier this week, Ethiopia hosted a regional East African summit, but the army boycotted it, claiming lead sponsor Kenya was biased.

Egypt, which has historically close ties with the Sudanese army, invited leaders of Sudan's neighbours to the Thursday summit, which aims to stave off foreign interference in the conflict and offer a new push for peace talks, two Egyptian security sources said.

A key priority for Egypt is to reassert itself on a file it feels excluded from by other regional efforts, diplomats said.

"All of our brothers in Sudan must uphold the supreme interest and keep Sudan's politics and unity away from external interference that seeks to achieve narrow interests," said Egyptian president Abdel Fattah al-Sisi.

Sisi presented an initiative to the group based on a ceasefire, opening of safe passages for aid, a comprehensive dialogue, and a mechanism to communicate with the warring parties.

The Egyptian plan aims to achieve a three-month ceasefire and open aid pathways by convening meetings with military and tribal leaders, taking advantage of long-term ties, the Egyptian sources said.

Some of the leaders attending appeared to welcome the Egyptian initiative.

But Ethiopian prime minister Abiy Ahmed called for it to align with the regional IGAD initiative announced earlier this week, which generally has the same aims.

"As neighbouring countries working to overcome our own internal challenges, we should not be perceived to impart wisdom to our sisterly nation, nor should we further complicate a fragile situation by extending its longevity," Abiy said.

Relations between Egypt and Ethiopia have been strained in recent years by a dispute over the giant dam Ethiopia has constructed on the Blue Nile.

The two leaders met on Wednesday, after Abiy last week said he would delay the fourth filling of the dam and ensure Sudan and Egypt received enough water, a conciliatory move.

Previous one-day and multi-day ceasefires were quickly violated, and were described by the UN special envoy Volker Perthes as an opportunity for the forces to re-position.

Speaking on Wednesday, he described mediation attempts as "emergency diplomacy".

"The two warring parties still think they can win the war so they accept diplomatic initiatives when they think it can help their aims," he said. Representatives for the RSF and army did not speak at the summit, but the army had previously welcomed it.

(Reporting by Aidan Lewis, Nafisa Eltahir, and Ahmed Mohamed Hassan in Cairo, Nadine Awadalla, Nayera Abdallah, and Tala Ramadan in Dubai, additional reporting by Julia Payne in Brussels, Dawit Endeshaw in Addis Ababa and Bhargav Acharya in Johannesberg; writing by Nafisa Eltahir; Editing by Alex Richardson)