The UN World Food Program (WFP) chief called Monday the relief efforts for quake-hit Haiti "one of the most complex operations" undertaken as the logistical operations to secure food distribution hubs has been extremely difficult.

"It will take some time for the food infrastructure to come on line," WFP Executive Director Josette Sheeran said here at a press conference at the UN Headquarters in New York.

Calling the situation "extremely challenging," Sheeran noted that one of the main priorities has been the creation of "orderly, secure distribution" sites for food where they are addressing such issues as adequate food escorts to ensure delivery.

"One of the most complex operations, if not the most complex operation we have faced," Sheeran said as she cited that due to Haiti's lack of infrastructure, it has been a "nightmare" getting food and supplies into the country.

Noting that there have been some episodes of food riots, Sheeran said that "we are concerned that the most vulnerable -- children and women can easily get overrun."

Addressing the methodology in the distribution of food, Sheeran cited that the priority for meals has been given to women and children.

One of the biggest challenges facing Haitians are working cooking facilities, where Sheeran noted that there is no cooking fuel, cooking apparatuses or even water to cook food in.

"We are putting out an appeal for ready to use food," Sheeran said.

Currently WFP has two daily flights that carry relief supplies into Haiti, in addition to warehouses that are set up in the Dominican Republic where trucks are stationed to bring supplies into Haiti.

But with a long delivery route to reach impacted areas due to road conditions, it has been "very problematic" in securing food distributions into the country.

WFP is currently assessing locations for main food hubs, where they will be placed strategically to meet those urgent food needs, Sheeran told reporters.

She noted that there will be a "continued large distribution of food until things come back on line," which could take longer than expected.

WFP has been in coordination with the UN peacekeeping mission, known as MINUSTAH, the Haitian government as well as other aid agencies toward relief efforts.