A coalition of opposition parties in Sudan, the National Democratic Alliance -- or NDA -- has appealed to the United Nations to intervene to end the country'scivil war.

The NDA urged the UN to set up a constitutional conference to find a solution to the conflict.

A leading NDA member , Mubarak al-Mahdi,told the BBC that any peace agreement would need international observers and forces to oversee it.

The NDA made its call in a letter to the UN Under-Secretary- General for Political Affairs, Kieran Prendergast, while he was visiting Sudan recently.

He went there at the request of aid agencies, who had asked the UN to try and resolve the conflict.Mr Prendergast is due to report to the Security Council later today.