KHARTOUM Aug 15 (Reuters) - Talks to secure a lasting ceasefire in Sudan's three warring regions under a road map for peace have collapsed less than a week after they began, the government's chief negotiator said on Monday.

Rebels have been fighting the Sudanese army in the southern regions of Kordofan and Blue Nile since 2011, when South Sudan declared independence. Conflict in Darfur, in the west, began in 2003 when mainly non-Arab tribes took up arms against the Arab-led government based in the capital Khartoum.

Last week, rebel and opposition groups agreed to a road map for ceasefire talks and political reconciliation brokered by the African Union and already accepted by the government - the first such agreement since the fighting began in the south of Sudan. Ceasefire talks began immediately after.

"Peace talks failed because of the lack of seriousness of the armed movements to reach a ceasefire agreement ... they are warlords invested in war," Ibrahim Mahmoud, the government's lead negotiator, said at Khartoum airport after returning from the peace talks in Addis Ababa.

"The main reason the negotiations broke down was the rebels' deal-breaking request that, following the ceasefire, humanitarian aid be delivered by airlift to rebel areas in South Kordofan and the Blue Nile from Ethiopia, South Sudan and Kenya. This was wholly rejected by the government delegation."

A spokesman for the Sudan People's Liberation Movement-North (SPLM-North) said the talks had failed because "the government didn't want peace ... we put forward major concessions but the government remained set on its positions and was unwilling to concede anything".

He said the rebels had requested that some of the aid come from outside of Sudan to deny the government the ability to cut it off as it had on previous occasions in Darfur.

The road map sets out a process for reaching a permanent ceasefire and provides for a national dialogue between the government and both political and armed opposition groups. It also included provisions for immediate humanitarian assistance.

The signatories included two of the most prominent rebel groups -- the Justice and Equality Movement (JEM) and the SPLM-North -- as well as the largest political opposition group, the Umma Party.

The Sudan Liberation Movement, a major rebel force in Darfur, and the Sudanese Communist Party refused to sign.

(Reporting by Khalid Abdelaziz; Writing by Lila Hassan; Editing by Eric Knecht)