* Cabinet to review defence spending cuts Tuesday -govt source
* Italian defense minister to outline cuts to lawmakers Wednesday
* Italy to cut order to 100 from 131 -newspaper
By Steve Scherer
ROME, Feb 10 (Reuters) - Italy seems certain to scale back its major investment in Lockheed Martin Corp's F-35 Joint Strike Fighter, heightening uncertainty over the troubled stealth jet's future.
Defence Minister Giampaolo Di Paola has said repeatedly since January that the country's originally planned order of the 131 supersonic warplanes by 2018 was being "reviewed" because military spending cuts were necessary as part of Prime Minister Mario Monti's austerity plan to shore up public accounts.
General Claudio Debertolis, secretary general of the Defence Ministry and the country's armaments chief, confirmed to lawmakers on Tuesday that cuts were expected.
"There will be a revision of this Joint Strike Fighter programme to align it with disposable resources," he said.
Italy will ask for about 30 fewer planes, Corriere della Sera daily reported on Friday, without citing its source. Panorama magazine gave the same number on Jan. 18.
Government sources and lawmakers told Reuters that it was premature to say how many of the F-35 fighters Italy will order because of uncertainty over the version of the aircraft designed for short take-off and vertical landing (STOVL).
This version is supposed to replace ageing Harrier jets on Italy's new hi-tech Cavour aircraft carrier.
On Tuesday Monti's Cabinet will examine the Defence Ministry's new spending plan that includes reducing F-35 outlays and personnel cuts, according to a government source. The minister will then detail the package to parliament on Wednesday.
The Pentagon's F-35 program office declined comment on Italy's plans, saying all of the partner countries would meet in Australia in March to discuss their production plans.
Uncertainty over the Pentagon's most expensive current arms programme is growing as participating countries cut or postpone orders, and flight testing continues.
Washington is expected to announce on Monday that it will postpone production of 179 planes over the next five years, bringing the total that would have been ordered between 2013 and 2017 down to 244 from 423.
In January the Pentagon announced $487 billion in defence cuts over the next decade.
"It's reasonable to do what the American government is doing, reduce the number of orders and spread them out over a longer time frame," said Federica Mogherini, secretary of the Italian Chamber of Deputies' defense committee and a member of the centre-left Democratic Party, the second-biggest bloc supporting Monti's technocrat government in parliament.
"It's not yet necessary to establish total number of planes we will order because costs are evolving, and all the technical problems have yet to be resolved," she told Reuters.
Some of the most significant technical problems concern the short take-off model, which has had engine trouble, and needed an early redesign due to excess weight. Recently, there were concerns about metal fatigue in a bulkhead, overheating of parts, and excess vibration in doors for an air input port.
Only the United States and Italy have so far said they plan to buy the STOVL version of the aircraft.
Australia has also said it is rethinking its plan to buy 12 of the radar-evading jets, and Turkey has put off buying two of them. Britain said earlier this month that it won't make a firm commitment on the number of planes until 2015. The other partners in joint construction of the plane are Denmark, Norway, the Netherlands, and Canada.
Italy is the third investor in the programme after the United States and Britain. Italy is in the process of ordering its first three planes for $240 million, Debertolis said on Tuesday.
Centre-left lawmakers called for defence cuts as Monti's "Save Italy" austerity measures kicked in this year, hitting Italians with smaller pensions and higher fuel costs, property and sales taxes aimed at eliminating the budget deficit by 2013.
Two newspapers aligned with the centre-left Democratic Party criticized spending on the F-35 jet programme in a series of articles during the first half of January.
State-owned Finmeccanica is one of the subcontractors on the project. Finmeccanica's Alenia unit will assemble the planes purchased by Italy, the Netherlands and Norway.
"Even if the order we make is much lower than 131 we started with, Italy's work on the aircraft is still guaranteed," Debertolis told lawmakers. "We could have a significant decrease in orders and still keep Italy's industrial role intact."