The United States is warning of a severe food crisis in two parts of Sudan — talk almost immediately dismissed by the Sudanese government.

The U.S. warning is contained in a letter, obtained by VOA, being circulated to members of the U.N. Security Council.

The letter accuses Sudan of preventing aid groups from accessing the states of Southern Kordofan and Blue Nile, where the government has been fighting rebel groups since the middle of last year.

The U.S. says that without substantial new aid to the two states, food security will deteriorate by March to an “emergency” level, where people will be unable to meet basic food needs, and eventually to famine conditions, the most serious form of food crisis as classified by the U.N.

Sudan's ambassador to the U.N. said Tuesday that the humanitarian situation in both states is “normal” and said Sudan is not impeding access to needy people.

He also renewed Sudan's accusation that neighboring South Sudan is assisting rebels in Southern Kordofan and Blue Nile.

U.N. officials and international aid groups have previously sounded warnings about the situation in the two states. Tens of thousands of refugees from the states have poured into South Sudan.

The rebels in both states favor the south, which split from the north to become an independent nation in July.