BBC World Affairs Correspondent
African leaders attending the major developed countries - or G8 - summit in the United States have urged greater attention to Africa, including the humanitarian crisis in Sudan's western Darfur region.
Janjaweed militia are accused of ethnic cleansing
But delegates to the summit will also be aware of the mixed signals coming from Sudan, Africa's largest country that has been at war for most of the years since independence in 1956.
Following marathon diplomatic efforts, including pressure from the US on all sides, an historic peace deal was signed in May between the main southern rebel group, the ethnic African SPLA, and the Arab-dominated Khartoum government.
The deal was the result of years of negotiations and has been hailed as a major breakthrough by most players.
UK International Development Secretary Hilary Benn, for example, who has just returned from a trip to Sudan, said it was a big step forward.
But a planned comprehensive peace settlement has yet to be finalised which, crucially, may have to include other conflicts in the vast territory of Sudan, which is roughly the size of western Europe.
Scorched earth policy
High on the agenda is the situation in Darfur, a region on Sudan's western border with Chad, where an estimated one million people have been made homeless by fighting between mainly African rebels and Arab militia.
The displaced people - mostly Africans - blame the Arab militia, or Janjaweed, for a scorched earth policy involving systematic killing, rape and looting.
The fighting has triggered a humanitarian crisis in Darfur
The UN refugee agency, UNHCR, says more than 150,000 of the displaced have fled to Chad, many to remote desert locations where delivering aid - shelter, food, medicines - is extremely difficult.
"We are facing a disaster," said UNHCR head Ruud Lubbers.
According to Mr Lubbers torrential rains due in the next few weeks will make access even more difficult.
The agency also faces a funding crisis, with its appeals for aid not being met by donors.
"We are tapping into our own resources and we are emptying our pockets," said Lubbers.
"We cannot say that this is the humanitarian crisis of the day and not fund the crisis."
'Worst humanitarian crisis'
The situation of displaced people inside Darfur is just as desperate.
Aid agencies complained that unnecessary customs delays and the slow delivery of government permits for aid workers to visit Darfur were hampering their efforts.
Hilary Benn said he raised this issue with Khartoum; he says he has been promised a relaxation of the customs regime for aid goods and the quicker delivery of visiting permits.
Whatever these marginal improvements might bring, UN officials and visiting foreign politicians are still describing Darfur as "the worst humanitarian crisis in the world today."
So, as the problem of the SPLA-government war apparently approaches resolution in the south, another Sudanese drama emerges in the west.
The former enemies in Sudan's southern conflict say they will now work together
Why is the situation in Sudan so intractable?
Why doesn't the international community, perhaps through the UN, move faster?
Many commentators have compared the world's relative inaction on Darfur to the failure to stop the genocide in Rwanda in 1994.
In fact, the situation on the ground in the two places is very different.
But the UN Secretary-General Kofi Annan (who was head of UN peacekeeping during the genocide) is sensitive to the analogy about delays.
During what have become almost ritual 'never again' speeches to commemorate the Rwandan pogroms, Mr Annan this April urged member states to help resolve the crisis in Darfur.
But in a report to the UN Security Council this week the secretary-general also set out the scale of challenge in Sudan were the UN to set up a monitoring mission to help implement a comprehensive peace settlement to cement the SPLA-Khartoum peace deal and encompass other conflicts like Darfur.
Sudan, he pointed out, is 35 times larger than Sierra Leone, which, until recently, hosted the largest UN peacekeeping force in the world at a cost of several billion dollars.
Mr Annan did not make the calculation, but the implication was clear.
If it took 17,000 troops to pacify Sierra Leone - where there was also a signed peace agreement - might it therefore take 35 times that number, or some 600,000, to do the same thing in Sudan?
Muslim north against Christian, Animist south
10,000 dead, 1m displaced
Arab government, militia against black Africans
The secretary-general also pointed out, with measured understatement, that there is "a total lack of infrastructure in the south," ensuring that "the United Nations will be working in the most demanding of circumstances."
As a sales pitch for a UN monitoring mission (no-one is seriously considering muscular peacekeeping) the report was sombre.
The distances involved are also huge.
The secretary-general's report, setting out a possible peace verification mission, said likely lines of communication for such a mission would be "equivalent in distance to that between the cities of New York and Houston with several planned sectors each the size of Austria or New York State."
But before the international community is asked formally to commit to a UN mission, the so-far elusive comprehensive peace settlement would have to be agreed.
'Positive and negative signals'
Here again the two major current conflicts (SPLA-government and Darfur rebels-government) clash.
Part of the reason why the Darfur rebels took up arms last year - apart from a long-standing resentment at perceived Arab domination of their region - was the limited nature of the SPLA-government talks in Naivasha, Kenya.
The Darfur rebels felt excluded from these talks which have now agreed detailed power and wealth-sharing arrangements between the SPLA and the government right down, for example, to the percentage of government jobs each side will be allocated.
In particular, the Naivasha agreement hammered out power-sharing deals for three oil-producing central regions claimed by the two sides as being in 'their' areas.
These are Abyei, Blue Nile and the Nuba Mountains.
The Darfur region, ominously, also straddles the north and the south.
Kofi Annan said in his report to the UN Security Council that "the catastrophic situation in Darfur is a problem that will make a Sudanese peace agreement much harder to implement."
The secretary-general concluded, in a formula which sums up the positive and negative signals coming from Sudan:
"To conduct a consent-based [UN] monitoring and verification operation in one part of the country while there is an ongoing conflict in another part would prove politically unsustainable inside the Sudan and internationally."