The Palestine Economic Development Company (PED) says repeated Israeli closures of the export terminal at al-Mintar (Karni) is jeopardising the livelihoods of 4000 Palestinian workers and their families.
The PED manages the Gaza Agricultural Project (GAP), which runs the greenhouses in the territory that were evacuated by illegal Israeli settlers in August and which earned their Jewish owners millions of dollars in export revenue.
The Karni cargo crossing, built in 1993 at the eastern end of Gaza, was built for Palestinians to import and export produce to Israel and the outside world. An estimated 800 lorries pass through it daily.
The agriculture sector in Gaza, a lifeline of income and employment in the impoverished and overcrowded territory, has incurred an estimated loss of €57 million ($68 million) during 35 days of recent Karni closures, it said.
"The entire Palestinian agricultural sector in Gaza is on the verge of collapsing due to the continuous Israeli closure of Karni," PED said.
Karni is the only crossing point for goods from the Gaza Strip and has been repeatedly closed by Israel in a tactic seen as collective punishment by the Palestinians.
"If the closure continues, the entire GAP project will eventually collapse," PED added in a statement.
Israel, on the grounds of security, regularly closes Karni, which was on Thursday closed for the ninth consecutive day.
On Wednesday, Palestinian officials said they had been told by Israel that the crossing would reopen on Thursday. Later, Israel said it would not reopen because Palestinians were still firing rockets toward Israeli points in the area.
Palestinian resistance fighters frequently fire homemade rockets towards Israel, but they rarely cause any casualties.
Salim Abu Safiya, director-general of the Palestinian Border Authority, said: "The continued closure is causing humanitarian and economic harm to the Palestinian people, and threatening a real shortage in food supplies."
Palestinian farmers had planned to dump hundreds of tons of produce that had nearly spoiled while waiting at the crossing to be exported to Israel and Europe.
Palestinians in Gaza can also suffer shortages of basic foodstuffs, such as milk, when the border is closed.