The sanctions -- which include restrictions on US exports, arms sales and financing to the government in Khartoum -- are to remain in place for at least one year, the US government said in a notice published Friday in the Federal Register.

Assistance to Sudan will be terminated "except for urgent humanitarian assistance and food or other agricultural commodities or products," it said.

However, certain measures will be partially waived because "it is essential to the national security interests of the United States" to do so, it added.

"The United States calls on the Government of Sudan to cease all chemical weapons use and uphold its obligations" under the Chemical Weapons Convention, an international treaty signed by nearly all countries that prohibits their use, the State Department said last month when it announced the sanctions.

The New York Times reported in January that Sudan's military had used chemical weapons on at least two occasions in remote areas its war with the paramilitary Rapid Support Forces (RSF).

Citing anonymous US officials, the newspaper said that the weapon appeared to be chlorine gas, which can cause severe respiratory pain and death.

Khartoum has denied using chemical weapons.

In practical terms, the effect will be limited as both Sudan's military chief Abdel Fattah al-Burhan and his adversary and former deputy, RSF leader Mohamed Hamdan Daglo, are already under US sanctions.

A power struggle between the army and RSF erupted into full-scale war in April 2023 with devastating consequences for the already impoverished country.

The conflict has killed tens of thousands of people and displaced 13 million, creating what the United Nations describes as the world's worst humanitarian crisis.