"They carry light personal weapons that are useful for internal policing but won't help fight a real army like Israel's," he said.
He added that Israel had been careful not to allow the Palestinian security forces to grow too strong, and had provided them with only limited intelligence.
"Ultimately we prefer to act by ourselves," he said.
Jeff Halper, an Israeli activist and academic whose recent book War Among the People examined Israel's military strategies, said it would be more accurate to describe Israel's security relationship with the Palestinians as "outsourcing."
"The important issue for Israel is that it retains control at all times," he told MEE. "It sub-contracts to the PA on the ground because it creates a buffer between Palestinians and the occupying forces and makes Israel's life easier."
The death of Abbas or collapse of the PA, he added, would create a huge vacuum, which would prove very difficult for Israel to fill.
"Israel might try to fill it with a strongman like Faraj or [Mohammed] Dahlan, but they would struggle to maintain their credibility, especially if there is no political horizon."
He said Israel could also try to recruit local Palestinian collaborators to control the main Palestinian cities, but if that failed, as seemed likely, Israel would have to reoccupy all of the West Bank directly.
Brom said that scenario would cause great difficulties for Israel: "We would need much larger forces operating in the territories and to be directly engaged in inhabited areas. That would be certain to create a lot more friction."
Additional reporting from Linah al-Saafin in Ramallah
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