President Barack Obama renewed U.S. sanctions on Sudan on Friday, acknowledging Khartoum had resolved disputes with South Sudan but warning that Darfur and other conflicts still impeded normal ties, the State Department said.

Khartoum reacted by accusing the United States of "double standards".

The order maintains several sets of U.S. sanctions imposed since 1997 that restrict U.S. trade and investment with Sudan and block the assets of the Sudanese government and certain officials.

Conflicts in Sudan's South Kordofan and Blue Nile states, which border South Sudan, threaten regional stability and the lack of humanitarian access to the regions remains "very serious", the State Department said in a statement.

Hundreds of thousands of people have fled their homes in South Kordofan and Blue Nile states since clashes between government forces and the rebel Sudan People's Liberation Movement North (SPLM-N) broke out more than a year ago.

Sudan and South Sudan, which broke away last year under a peace deal that ended a decades-long civil war, signed deals in September to resolve border and security issues left over from their partition.

But issues such as the status of the contested Abyei region also posed a threat to security, the State Department said.

"Addressing these concerns is necessary for a peaceful Sudan and would enable the United States and Sudan to move towards a normalized relationship," it said.

Khartoum criticized the sanctions decision which it said was aimed at stymieing development in the country and pressuring Sudan to make concessions to American interests in the region.

"The American administration has acknowledged more than once that Sudan has honored its commitments but the American administration, time and again, has withdrawn from its promises ... to lift the sanctions," the foreign ministry said.

Many Sudanese officials expected the United States to take steps to normalize relations with Khartoum after the South seceded peacefully last year, and have been disappointed by the renewal of the trade sanctions.

More than 2 million people died in Sudan's civil war, fought between north and south for most years between 1955 and 2005 over religion, ideology, ethnicity and oil.