In a departure from its earlier position, Sudan on 12 June accepted that such a force could be deployed in its troubled western region of Darfur.
HRW, in a statement ahead of a planned trip by Security Council members to Africa, including Sudan, from 14 June, called for greater pressure on the Sudanese government: "It is essential that the Security Council ensures that the Sudanese government's commitment to the 'expeditious' deployment of the full AU-UN force is matched by its immediate action."
"The Sudanese government is still getting away with murder in Darfur," said Peter Takirambudde, Africa director at HRW. "The Security Council needs to tell Khartoum to stop using delaying tactics and start protecting its people."
Sudan's acceptance of the hybrid force was announced at the end of a meeting in the Ethiopian capital, Addis Ababa, where two options were outlined regarding the size of the proposed force's military component: plan one would have 19,555 troops deployed, while option two would see 17,605 troops sent in. The police component would require 3,772 officers.
Mutrif Siddig, under-secretary in the Sudanese Ministry of Foreign Affairs, said: "If we are to reach the requirements of the hybrid operation, the situation in Darfur will change dramatically. This does not minimise the need for political support for the operation because the political process will address the root causes of the problems and lay a peaceful foundation for the resolution of the conflict in Darfur."
However, he indicated that Sudan would prefer that the composition of the hybrid forces be predominantly African. "The recruitment of the operation [should] give the priority to African staffing in all its areas: the military, the police and the civil component. But if we do not meet the needed number or requirement, the three parties will agree to complete the rest from agreed countries outside Africa."
"The options will be left to a decision by the AU and UN, based on a number of elements including the availability of troops and assets," AU Peace and Security Commissioner Said Djinnit explained. "The option of 17,000 relies more on transport [and] air mobility. If we do not have that asset, then we have to have more troops."
The hybrid operation is the third phase of a three-step process to replace the existing but under-resourced AU Mission in the Sudan (AMIS), which has been unable to end the fighting in Darfur. The mission is 7,000 strong.
The first step was the US$21 million 'light support' package which had a logistics, personnel, equipment and humanitarian aid component, while the second step was the $289.9 million 'heavy support' package to AMIS.
The Addis Ababa agreement comes after months of disagreement over proposals to boost international peacekeeping efforts in Darfur. The conflict, which started in 2003, has seen more than two million people - nearly one in three in Darfur - flee their homes to seek shelter in camps. Another 230,000 refugees are in neighbouring Chad.
Last week, Oxfam reported that increasing violence in the region had cut aid workers' access to affected civilians to its lowest level since the early days of conflict.