The official levelling of war crimes charges against Sudanese President Omar Hassan Ahmad al-Bashir has been welcomed in many quarters, but fears remain the decision could cause an escalation of violence in Darfur and more misery for millions of long-suffering displaced Darfuris.

International Criminal Court (ICC) Prosecutor Luis Moreno-Ocampo on Monday requested an arrest warrant on al-Bashir for crimes against humanity and genocide committed in Sudan's restive western province, where the UN says up to 300,000 people have been killed and 2.5 million displaced by five years of ethnic conflict.

The response by the joint United Nations-African Union peacekeeping mission UNAMID was to begin pulling non-essential staff out of Darfur on Tuesday amid concerns that members of the mission, already a target for deadly attacks, would come under further fire.

General Martin Luther Agwai, UNAMID Force Commander said that force protection levels and patrolling would remain the same and that peacekeepers would 'continue to assist humanitarian organizations to do their job.'

The problem is that the current force is unlikely to be able to cope should the situation escalate. UNAMID - which has less than 10,000 of the planned 26,000 military personnel in place - is already struggling to fulfill its peacekeeping role.

Sudan has continued to block the full deployment of troops through various means, including demanding only African peacekeepers.

There are also lingering suspicions that the government is harassing and even attacking UNAMID through the proxy weapon of the Arab Janjaweed militia.

Khartoum has long been accused of using the Janjaweed to commit atrocities against Darfur's black population and suppress the rebels, who took up arms against what they called decades of neglect and discrimination by the Arab-dominated government.

Seven peacekeepers died last week in an attack believed to have been carried out by the Janjaweed and many in UN circles think the militia could step up raids as the government seeks to punish UNAMID for the ICC's actions.

UN Secretary General Ban Ki-moon on Monday highlighted the fact that the ICC is an independent institution and called on Sudan to cooperate with UNAMID.

However, militiamen are not likely to bother with such distinctions, and Sudan issued a stark warning about the consequences of the possible arrest warrant.

'Our reading of this move by Moreno-Ocampo is that it will lead the peace process to a disaster,' Sudan's UN Ambassador Abdalmahmood Abdalhaleem Mohamad said at UN headquarters in New York.

He urged the UN to choose between the ICC or peace in Darfur: 'You cannot have it both ways, the choice is very clear.'

But UN staff on the ground are not just worried about government militia. They are worried that rebel groups, emboldened by the charges, could soon launch a series of attacks.

'People are a little tense and there has been a lot of catastrophic thinking,' a source within the UN in Darfur told Deutsche Presse-Agentur dpa. 'Over the coming days, it is possible the rebel forces, which have been gathering faster than expected, might do something.'

An escalation in violence, whether directed at UNAMID or not, will only mean more misery for the battered population of Darfur, millions of whom are living in refugee camps and are entirely dependent on humanitarian aid.

'The problem...is that the Prosecutor's legal strategy also poses major risks for the fragile peace and security environment in Sudan, with a real chance of greatly increasing the suffering of very large numbers of its people,' the International Crisis Group (ICG) said in a statement.

However, the ICG did sound a note of hope.

While Sudan does not recognize the ICC - it last year refused to extradite a government minister and a militia leader wanted by the court - the ICG believes there is an outside chance Moreno-Ocampo's request could move the peace process forward.

'It may be that the increased pressure...will lead it (Sudan) to take long overdue steps to cease all violence and implement genuine and credible measures to resolve the Darfur crisis.'