Palestinians in the cut-off Gaza Strip could face food shortages within two weeks, the United Nations warned. The U.N. Office for the Coordination of Humanitarian Affairs said in a report issued Wednesday that supplies of necessities like flour, rice and oil to Gaza could be choked off entirely unless Israel reopens a commercial crossing that was sealed after Hamas seized control of the territory last week. “The reopening of Karni crossing is vital to prevent general food shortages in 2-4 weeks,” the report said. Israel, with foreign support, has declared it will isolate the Hamas administration in Gaza while maintaining vital supplies to the general Palestinian populace. Several truckloads of food and medical supplies were allowed into the territory Tuesday.