A reduced Israeli purchase may dent international confidence in the Lockheed Martin Corp plane and manufacturer efforts to lower the unit price because of advance orders.
Israel bought 19 F-35s for $2.75 billion in 2010, with delivery scheduled between 2016 and 2018. Defense Minister Moshe Ya'alon, visiting the United States last month, agreed a preliminary deal for 25 to 31 more planes subject to approval by the ministerial committee for defense purchases, sources said.
Steinitz, one of the committee's members, told Reuters there was majority opposition to the scale of Ya'alon's order and preference for a smaller purchase of 10 to 15 planes. A final decision is expected in the coming days.
The ministerial committee was leaning towards approving a smaller order now and reexamining the deal in three years, when the first order of planes arrive and go into use.
While declining to go into detail about the closed-door discussions, Steinitz cited misgivings about whether the F-35's range, payload and manoeuvrability would suit Israel's needs. The Israelis are also husbanding a defense budget which, though buoyed by some $3 billion in annual US grants, faces cuts.
Other concerns include the fact the jet's electronic systems are American-made, and Israel will not be able to equip it with Israeli-made systems. This would also have ramifications on exports of the Israeli Military Industry to foreign air forces.
The Americans can also supervise the use made of the plane, which led Britain to threaten to cancel its purchase.
The decision is a blow to the security establishment and to the Air Force. According to ministers who took part in the discussions, this is the first time in years the ministerial committee refuses to automatically approve a defense purchase request.
The ministers were angry that the defense establishment announced the purchase as a "done deal."
"We are not the Defense Ministry's rubber stamp," Steinitz said.
Other than Steinitz, who headed the committee in the absence of Prime Minister Benjamin Netanyahu, Agriculture Minister Yair Shamir, a former fighter pilot in the Air Force, and Economy Minister Naftali Bennett also held reservations about the deal.
Ya'alon's spokesman had no immediate comment.
The ministerial committee, headed by Prime Minister Benjamin Netanyahu, has met four times to discuss the F-35 purchase, twice deferring deadlines on a decision.
The delay could mean Israel incurring penalties on Citibank loan guarantees it had arranged to pay for the F-35s. Terms for the loans were due to expire on November 15, defense sources said.
The 2010 F-35 deal gave Israel the option of buying 75 planes in total - three squadrons. This is one of the biggest deals in the country's history which, if completed in full, will cost $15 billion: each jet would cost $142 million even before it is fitting with additional systems.
But Steinitz's numbers mean Israel will have fewer than two squadrons in the forseeable future, an operational challenge for its air force, which has been tasked with a multitude of regional missions including threatened strikes against Iran's nuclear facilities.
While most of the funding for the planes will come from the $3 billion worth of American military aid package, the ministers said such a purchase will essentially mortgage the aid package on the expense of other purchases.
Another Israeli official linked the resistance Ya'alon was meeting from cabinet colleagues to the Operation Protective Edge in Gaza, which ended inconclusively and triggered calls for more investment in armoured troop carriers and munitions.