The US State Department suspended talks with the government of Sudan on Thursday after a Sudanese helicopter fired rockets at a crowd of thousands gathered to receive aid from a World Food Programme (WFP) relief mission.

The attack, which took place a day before in the village of Bieh located in an area where European and Asian companies have been exploring and drilling for oil, killed at least 17 people and injured dozens more, according to the Rome-based WFP, which said it had notified Khartoum in advance of its plan to distribute food there.

''Such attacks, deliberately targeting civilians about to receive humanitarian aid, are absolutely and utterly unacceptable,'' said WFP director Catherine Bertini. ''This attack - the second of this kind in less than two weeks - is an intolerable affront to human life and humanitarian work.''

The incident took place as Washington pursued talks with the National Islamic Front (NIF) regime on ending Sudan's 19-year-old civil war. The State Department, which has had warm words for Khartoum over its reported cooperation in the US ''war on terror'', issued an uncharacteristically blunt reaction.

Calling it part of a ''pattern of senseless and brutal attacks by the government against innocent civilians,'' the State Department said ''these attacks raise serious questions about the Sudanese government's commitment to peace and the lives of its people. We have demanded from the Sudanese government a full and complete explanation of what happened.''

''In addition, we have asked for an explanation of how one part of the government can negotiate with the United States an agreement to end attacks against civilians while another part of the government is deliberately targeting civilians,'' the statement continued.

''Until we receive a full and complete response,'' all discussions with Khartoum on a new US and European-led peace initiative will be suspended, it added.

Officials did not say whether Washington also would delay this weekend's scheduled deployment of US monitors who, with counterparts from Europe, are to oversee a ceasefire between Khartoum and the Sudan Peoples Liberation Movement/Army (SPLM/A) in the Nuba Mountains.

Critical moment

Wednesday's attack and the US reaction have come at a critical moment in the peace initiative, designed to achieve a cease-fire and eventually a permanent peace agreement between the mainly Arab NIF government in Khartoum and the predominantly black African and Christian or animist population of southern Sudan, led by the SPLM/A.

The war is believed to have killed more than two million people, mostly southern Sudanese, and to have forced some four million to flee their homes.

President George W Bush's special envoy on Sudan, former Senator John Danforth, has proposed that both sides agree to four ''confidence-building measures'' that could constitute the basis for broader peace efforts.

While Khartoum last month accepted three of the measures - the establishment of ''tranquility zones'' for vaccination drives in the south; the creation of an international commission to determine Khartoum's role in the abduction and enslavement of southerners by government-backed tribal militias; and an internationally monitored ceasefire in the Nuba Mountains - it has thus far rejected the fourth, an unconditional halt to the its bombing of civilian areas in the south.

Danforth is supposed to write a report for Bush early next month on the prospects for further progress in the peace process. That report will determine whether Washington will remain engaged in mediation efforts.

The Bush administration has been under pressure on Sudan from all sides. A broad coalition of groups from the Christian Right to the Congressional Black Caucus have pushed for tough sanctions against Khartoum, including barring foreign companies with investments in Sudan's oil sector from US stock markets, as a way to get Khartoum to negotiate seriously on a peace agreement that would guarantee the south self-determination.

Khartoum is currently earning about US$500 million a year from oil exports, much of which it uses to buy more weapons, particularly combat helicopters, with which to prosecute the war.

On the other hand, many US businesses, as well as senior administration officials, strongly oppose the proposed sanctions despite the fact that Washington has banned most US trade and investment in Sudan since the early 1990s, when the State Department accused it of supporting international terrorism.

Al-Qaeda chief Osama bin Laden lived and worked in Khartoum for five years, from 1991 to 1996.

After last September's terrorist attacks in the United States, however, Khartoum, apparently fearful that the Bush administration would add Sudan to the list of possible targets for retaliation, rounded up about two dozen people allegedly associated with the al-Qaeda network and opened many of its intelligence files for inspection by the US Central Intelligence Agency (CIA) and Federal Bureau of Investigation (FBI).

At the same time, it expressed stronger interest in Washington's involvement in mediating with the SPLM/A. Encouraged, Danforth and diplomats from several European countries including Britain, Norway and Switzerland, last month presented the confidence-building measures as a first step.

Profound regrets

Sudanese Foreign Minister Mustafa Osman Ismail came to Washington just last week to pursue talks with Danforth and others. In an interview with allAfrica.com,' he expressed ''profound regrets'' for a bombing by helicopters that had taken place after a WFP food drop in the southern town of Akeum the week before, insisting that it resulted from a technical error. Two children were killed, and a dozen others wounded.

''Of course, we don't deliberately target civilians,'' he asserted.

Several days later, the humanitarian group Doctors Without Borders (Medicins Sans Frontieres, or MSF) confirmed that a similar attack on the village of Nimne in the oil-drilling area had taken place on the same day as the one on Akeum. The Nimne attack killed five people, including a 20-year-old MSF health worker, wounded many more, and scattered the population into the surrounding countryside.

Wednesday's attack, which the SPLA said involved four helicopters, appears to mark a major escalation by Khartoum, if not a harsh slap at Danforth and US peace efforts.

Washington was already moving to engage Khartoum's opposition more directly. During a visit here last week, the National Democratic Alliance (NDA), which includes the SPLM, received the first million-dollar installment in a long-delayed three-million-dollar aid package to help beef up its political representation in East African capitals, as well as an invitation for an NDA delegation, headed by SPLM chief John Garang, to visit here in mid-March, according to knowledgeable sources.

Khartoum also was shaken up several weeks ago when, without checking first with the NIF government, US naval forces boarded a Sudanese vessel in the Red Sea as part of its mission to intercept boats suspected of carrying al-Qaeda personnel from Afghanistan. ''They thought they were allies in the war against terrorism,'' said one source. (IPS)