Rosemary DiCarlo called on the national army and so-called Rapid Support Forces to lay down their arms, more than five months after they began facing off in the streets of Khartoum.

She told a high level ministerial event on The Cost of Inaction in Sudan taking place at UN Headquarters in New York that only a return to the negotiating table, “to advance a meaningful ceasefire that would lead to a durable cession of hostilities”, could end the suffering.

The fighting has now destabilised the entire region, leading to the deaths of more than 5,000 Sudanese, and displacing millions both within the African nation and across seven national borders.

More than 7 million on the run

She said Sudan was now home to the highest number of internally displaced anywhere in the world, with at least 7.1 million uprooted.

“Political inaction on Sudan has already exacted a heavy cost…In addition to essential humanitarian action we also need an increase in effective diplomacy” Ms. DiCarlo added.

She called on the international community to do more to bring about a ceasefire and political settlement.

"More than 6 million Sudanese are one step away from famine. These numbers will keep growing, as long as the guns keep talking”.

UN relief chief Martin Griffiths told the meeting that if you want to know the cost of inaction, “you need look no further than the price the Sudanese people have already paid”.

‘At least 13 mass graves’

The violence has become increasingly ethnic in nature, especially in the historic cauldron of instability, Darfur. Reports suggest there are “at least 13 mass graves in places such as El Geneina.

The health system has almost totally broken down, and some 1,200 children have died from malnutrition and preventable diseases such as measles.

He said humanitarians were doing everything they can “to bring the response up to scale and speed.

Off target

So far, his humanitarian affairs coordination office OCHA and partners have reached around 3.5 million with critical aid, “but this amounts to only 19 per cent of the 18 million people we are targeting”.

Sudan has become perhaps the most dangerous and complex operating environment in the world, coupled with access difficulties and bureaucratic roadblocks.

The Emergency Relief Coordinator called for a concerted international push to get lifesaving help into the areas where it is needed.

“It is needed now, it was needed yesterday, and it will be needed tomorrow”, he told ministers.