KHARTOUM, Sudan — Sudan’s ruling party warned yesterday there will be more violence in Darfur if the country’s president is indicted for crimes against humanity and genocide as hundreds of people rallied in Khartoum to show their support for the longtime leader.

A prosecutor at the International Criminal Court is expected to seek an arrest warrant today charging President Bashir with orchestrating violence in Darfur that has left hundreds of thousands of people dead since 2003.

In Sudan, the ruling National Congress Party called the case against Mr. Bashir “irresponsible cheap political blackmail” that has no legal basis, according to a statement from the party that was broadcast on state TV. It also warned there would be “more violence and blood” in Darfur if an arrest warrant is issued against the president, TV reported.

Mr. Bashir huddled with Cabinet ministers and advisers yesterday, weighing how the government would response to any action taken by the ICC. Sudan has also asked the Arab League for an emergency meeting of Arab foreign ministers.

Outside the meeting, hundreds of Sudanese, many carrying flags and pro-government banners, demonstrated to show their support for Mr. Bashir, who seized power in a 1989 coup. Others held signs ridiculing the ICC and its prosecutor, Luis Moreno-Ocampo of Argentina. “Ocampo is a plotter against Sudan’s people,” one banner read.

On Saturday, a government spokesman said Mr. Bashir’s indictment would be “disastrous” for the region and could affect the work of humanitarian organizations in Sudan.

Mahjoub Fadul Badry did not specify what actions might be taken, but there are fears the charges could provoke reprisals against international aid workers and the U.N.-African Union peacekeepers that are already experiencing difficulties in doing their work.