"The United States has worked intensively with partners to provide relief to Sudan... today we are announcing another roughly $200 million," he said at a UN Security Council meeting on Sudan.
The World Food Programme warned Thursday that Sudan risks becoming the world's largest hunger crisis in recent history, with 1.7 million people across the country either facing famine or at risk of famine.
Sudan has been ravaged by 20 months of fighting between the regular army and the paramilitary Rapid Support Forces (RSF).
OCHA operations director Edem Wosornu told the Security Council $4.2 billion would be needed to support the needs of Sudan's people next year.
"The volume of humanitarian aid reaching people in need remains a fraction of what is required," she told the Council.
"Ultimately, the only way to end this cycle of violence, death and destruction is for this Council to rise to the challenge of delivering lasting peace in Sudan."
Nearly all of Darfur is now controlled by the RSF, which has also taken over swathes of the neighboring Kordofan region as well as much of central Sudan.
The regular army retains control of the north and east, while the capital Khartoum and its surrounding cities are a battleground between the warring parties.
The war has killed tens of thousands and displaced more than 11 million, creating what the United Nations describes as one of the worst humanitarian disasters in recent memory.
Both the army and the RSF have been accused of indiscriminately bombing medical facilities and civilians, as well as deliberate attacks on residential areas.
