Some fear that the Sudan-South Sudan accords signed last month could make the humanitarian crisis even worse. With the demilitarized border agreement in place and oil revenues expected to bolster its depleted state coffers, Sudan appears primed for a heavy military offensive in the rebel areas. Hunger is expected to be among the weapons, as it is has been in the decades of the region’s brutal civil war.

A letter last month from Nuba representatives addressed to former South African President Thabo Mbeki, who’s been mediating peace talks between Sudan and South Sudan, said the 2005 peace deal hadn’t resolved the issues they faced. It warned that the Nuba people were facing "another vicious circle of never-ending wars and sufferings."

U.S. efforts to persuade Sudan to allow in international aid have failed so far, thanks in part to the icy relations between the countries, made worse by the attack last month on the U.S. Embassy in Khartoum, which prompted the Obama administration to withdraw its diplomats.

The U.S. is supporting a joint United Nations, African Union and Arab League plan – known as the tripartite proposal – to open humanitarian access, but Sudan is refusing to implement the deal.

With that plan stymied, the U.S. rolled out a clandestine plan to send thousands of tons of food from South Sudan by road, until rains made the sole dirt track north impassable in July.

U.S. officials haven’t publicly acknowledged the cross-border aid operation, but in an interview last month with Fox News’ Greta Van Susteren, the Nuba Mountains rebel leader, Abdelaziz al Hilu, credited the American food aid with saving lives.

“Thanks to the American people, to the American government, that they have channeled food somewhat, and they saved thousands and thousands of lives. But it was not enough. It was not enough. And the rainy season also stopped the whole operation, and the suffering has increased," he told Van Susteren during a visit to Washington with other leaders of the Sudan People’s Liberation Movement-North.

This fall’s harvesting season in the Nuba Mountains is expected to ease the food shortage, but only temporarily. Rains were poor, and the fact that thousands of people fled into the mountains as protection from government bombing raids means that many fields were never planted.

"The food situation overall looks fairly bleak for the next year," Catena said in an email. "We’re anticipating food shortages throughout the year and high prices for the small amount which will be available in the market, a repeat of last year."

U.S. special envoy Princeton Lyman said he’d keep pushing for aid to reach the rebel-held areas – some way, somehow.

"What we want is the tripartite agreement. Because that is the best way to get the most aid to the most people," Lyman said Sept. 27 in a phone interview from Ethiopia, after Sudan and South Sudan signed their deal. "The question for the international community is what do we do if that doesn’t happen?"

Asked whether the U.S. will continue sending food after the road from South Sudan reopens, Lyman demurred.

"This is part of what we have to discuss in New York,” he said, referring to the United Nations. “That is not the best and most effective way of doing this."