Alex de Waal, a Sudan expert at Harvard University in the US, told the BBC's Network Africa programme the pre-trial chamber of the ICC was expected to issue an arrest warrant for President Bashir.
He said the only real doubt is whether it will be for genocide or if the tribunal will stick to the less controversial charges of war crimes and crimes against humanity.
But an indictment warrant would be "pretty toothless", he added, as the ICC does not have a police force and it would be delivered to Sudan's government, which is unlikely to execute it.
Salva Kiir, Sudan's vice-president and leader of the south of the country, has issued a statement describing the possible indictment as "unnerving".
He said all Sudanese were hurt by the accusations against President Bashir, and urged southern Sudanese to refrain from demonstrations that could heighten tensions.
He called for diplomatic and political efforts to defuse the crisis.
African Union and Arab League states are calling for a year's delay to any indictment, warning it could plunge Sudan into deeper crisis - just as a new round of peace talks begin.
The five permanent UN Security Council members, who have veto power, are said to be divided on the issue.
The United States, France and Britain are supporting the call to bring President Bashir to book immediately for his alleged crimes.
Sudan's president remains defiant
But China, which has strong economic ties to Sudan, and Russia would likely support a delay, according to diplomats.
Meanwhile, there are concerns about a military build-up along the Sudan-Chad border.
The two countries have accused each other of giving shelter to rival rebel groups, and there are concerns that the actions of the ICC could have violent consequences.
The war crimes court has already issued two arrest warrants - in 2007 - for Sudanese Humanitarian Affairs Minister Ahmed Haroun and the Janjaweed militia leader Ali Abdul Rahman. Sudan has refused to hand them over.
The ICC - the world's first permanent war crimes tribunal which started work in 2002 - is also pursuing indictments for three Darfur rebel commanders accused of killing a dozen African Union peacekeepers.
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