President Joe Biden has issued an executive order authorising sanctions against Sudan, saying the fighting must end.
Mr Biden called the violence a tragedy and a betrayal of the Sudanese people.
He said the violence in Sudan was an “unusual and extraordinary threat to the national security and foreign policy of the United States”.
Earlier, the director of National Intelligence, Avril Haines, told a US Senate committee that the conflict was likely to be protracted, as both sides believed they could win militarily and had few incentives to negotiate.
The latest ceasefire has failed to hold, with heavy fighting continuing in the capital Khartoum, as well as the adjoining cities of Omdurman and Bahri.
The World Food Programme has estimated that more than $13m (£10.3m) worth of food aid destined for Sudan has been looted since fighting broke out last month.
The WFP said pillaging in the country was rampant.
The UN children’s agency, Unicef, warned the situation was teetering toward catastrophe, with youngsters increasingly caught in the crossfire.