The parliament will discuss on Saturday whether to refuse to hand over Darfur war crimes suspects to an international court based in The Hague, said Aljazeera's correspondent in Khartoum, Al-Tahir al-Maradhi.
Sudan's Foreign Minister Mustafa Usman Ismail criticised the UN Security Council and Secretary-General Kofi Annan, accusing him of inciting Darfur resolutions.
During a session at Sudan's parliament, Ismail warned that Darfur rebels should not pressure the government through the Security Council.
Ismail said he expected the parliament to make a decision on Sunday.
Sudanese leaders will also begin on Saturday the drafting of an interim constitution expected to seal a peace deal with the south. Major opposition groups plan to boycott the meeting.
Inauguration of the process coincides with the deployment of international forces to support the 9 January peace accord the government signed with the Sudan Peoples' Liberation Movement (SPLM) in Kenya.
Foreign Minister Mustafa Ismail
criticised the UN Security Council
The first 12 United Nations troops, all from Nepal, arrived early this week and more will follow over the coming days, according to the UN mission in Sudan.
The UN Security Council in March approved the deployment of 10,000 UN troops to shore up the north-south peace agreement that ended 21 years of fighting that killed 1.5 million people.
Sudanese President Umar al-Bashir and SPLM leader John Garang will address the 60-strong National Constitutional Review Commission's (NCRC) inaugural session on Saturday during a ceremony in Khartoum, officials said.
Garang will not be present in the capital, which he has not visited since 1983 when his movement declared war against Khartoum, demanding greater autonomy for the animist and Christian south from the Arabised Muslim north.
He will address the gathering by telephone, officials said.
Sudan's ruling National Congress (NC) party and the SPLM decided to proceed with preparations to inaugurate the NCRC after they failed to persuade the country's main opposition groups to sign up.
Ismail said on Wednesday the meetings would begin "in spite of the absence of some political parties".
A new constitution is crucial because it would clear the way for the formation of a national unity government and usher in a six-year interim period called for in the January peace accord.
Ismail's comments came as a six-member team of NC and SPLM officials arrived in Khartoum from Cairo after fruitless meetings with the National Democratic Alliance, a grouping of mostly northern opposition forces.
SPLM leader John Garang failed
to bring other rebels to the table
The NDA, Sudan's principle opposition bloc, represents the most formidable political challenge to the NC and includes the Democratic Unionist Party (DUP), the country's second-largest political movement.
It signed an initial agreement with the government this year but refused to join the process until the signing of a comprehensive agreement.
Status of forces
NDA officials said some issues remained to be resolved such as the status of their forces and further discussions on a permanent constitution.
"We cannot participate in this process because the issue of a constitution is an item on the agenda of our dialogue with the government," said al-Tom Haju, the DUP's representative in the NDA.
Haju held Khartoum responsible for the deadlock in the process.
"The government said it would return to the negotiations only after we set a date for the signing of a final agreement. We believe a date should be set after the conclusion of discussions on all issues," said Haju.
A last-ditch effort by Garang to bring the NDA on board during a meeting with DUP chairman and NDA leader Muhammad Usman al-Mirghani in the Eritrean capital, Asmara, on Wednesday also failed.
In Khartoum, the Umma party of former prime minister al-Sadiq al-Mahdi and 10 other opposition groups issued a joint statement saying the makeup of the NCRC was not representative of the country's political landscape.
"The constitution is a document that expresses the consensus of the nation and all ingredients of the Sudanese people and should guarantee the rights of all parties, not only those of specific parties," the statement said.
The Umma and others object to the insistence of the NC and SPLM on applying general power-sharing quotas agreed upon in the peace agreement, which give them 52% and 28% of the seats respectively.
The arrangement leaves other northern and southern parties a paltry 20% and no power to block decisions.
Hasan al-Turabi's group has
voiced its concerns
The Islamist opposition Popular Congress party of jailed leader Hasan al-Turabi has expressed reservations but agreed to take part in the constitution-drafting process.
Only a few groups, mostly breakaway factions of the major political parties and the Muslim Brotherhood, widely considered an extension of the ruling NC party, have agreed to join the NCRC without conditions.