WFP Executive Director Ertharin Cousin arrived Monday in Khartoum as part of a three-day visit that includes a stop in South Sudan.
"Sudan is one of WFP's largest and most complex operations, providing food assistance to more than 4 million people affected by conflict, displacement and chronic under-nourishment," the organization stated.
WFP, in early August, said it was "pulling out all the stops" in South Sudan by airdropping more than 2,000 tons of food in parts of the country. The country is among the world's poorest and the situation there is complicated by ongoing skirmishes with Sudan.
Jamal al-Fadil Faraq Allah, a Sudanese driver for a staff member with the U.N. World Food Program, was killed last week by unknown assailants in the restive Sudanese state of South Kordofan.
Cousin is expected to meet with South Sudanese authorities Tuesday.