The conference is part of a series of donor nation meetings that began in Oslo in 2005, just after a comprehensive peace agreement ended fighting that cost two million lives, many from famine and disease.
That conference brought pledges of $4.5 bn in aid.
"The comprehensive peace agreement ended one of the most bloody wars in Africa, and a 21-year war ... in the biggest country in Africa," Erik Solheim, Norway's aid minister, said.
"Though there are difficulties as we all know, there are a number of provisions in the peace agreement that have been implemented."
Solheim opened the meeting by calling for a moment of silence in memory of Sudanese officials, including Dominic Dim Deng, southern Sudan's defence minister, who died in a plane crash last week.
Salva Kiir, president of southern Sudan, cancelled plans to attend the meeting because of the crash.
Most countries are expected to announce their pledges at a special session near the end of the meeting on Wednesday.
"It is evident that much has been accomplished," Taha said.
"However, we honestly feel what has been offered so far does not satisfy our national expectations and aspirations with the colossal demands of post-conflict reconstruction and recovery."
Norway helped broker the 2005 peace accord, with northern and southern Sudan in an interim peace period due to end with a 2011 referendum on whether the south will secede.
The war pitted the Arab Muslim-dominated government in Khartoum against militants fighting for greater autonomy and a larger share of the country's wealth in the largely African animist and Christian south.
Despite the peace pact, fighting has raged on in Sudan's troubled Darfur province.
Thirteen people including seven children were killed when Sudanese government bombs hit a primary school and a busy market place in Darfur, in the latest violence reported by two aid organisations on Monday.
But Solheim said the on-going violence must not be allowed to stand in the way of the broader peace effort.
"This is an opportunity to discuss the progress of the peace process, but it is also a donors conference," said Solheim.
The Sudan Consortium, as the donors group is called, is chaired by the Sudan government of national unity, the government of southern Sudan and the Norwegian organisers, the World Bank and the United Nations.