* Govt may lower contributions to 5 pct, from 7.3 pct now
* Poland keen to prevent its debt from breaching 55 pct/GDP
* Move comes after Hungarian pension shift criticised
* Investors express worry over fiscal "slight of hand"
By Gabriela Baczynska
WARSAW, Dec 1 (Reuters) - Poland may be the latest eastern member of the EU to fiddle with a successful pension reform in a bid to ease short-term debt problems that risks raising future debt levels and driving local markets lower.
A government source told Reuters there are plans to replace some of the cash contributions to private pension funds with non-tradeable bonds as Prime Minister Donald Tusk's cabinet seeks ways to reduce the deficit ahead of a 2011 election.
The moves, like more aggressive steps being taken in Hungary, are part of efforts by the eastern Europeans to deal with temporary additional costs created by much-praised 1990s reforms of their pension systems.
The European Union has declined to give Hungary, Poland and others further leeway on how their deficits and debt are assessed in light of the reform costs, which will eventually drop off government spending.
"There is a consensus within the government to lower cash transfers to OFEs (private pension funds)," the Warsaw source said under condition of anonymity.
"We should have the key decisions over the course of the next 10 days and we will be ironing out the details."
The source said one of the options included lowering cash transfers to OFEs to 5 percent from the current 7.3 percent.
"But it is possible that the 2.3 percent difference will be compensated in OFE-dedicated bonds. For the timespan of the most difficult year, or two, we may also change the proportion and have more in bonds and less in cash," the source added.
"We are still discussing whether the bonds would be tradable or not, but for now we seem to lean to the non-tradable option."
Budapest's new government has gone as far as to propose a nearly complete turn around which brings private fund assets back into the state system, prompting outrage from the industry and concerns that in the long run it will lead to sharply higher debt.
The Polish proposals do not go as far that, but still run the risk of upsetting markets already unnerved by the euro zone's debt troubles and Warsaw's failure to show willing on budget cutbacks of its own.
"The EU's Maastricht (budget) criteria have been abused by virtually everybody, and look at the kind of mess that we've gotten into," said Nigel Rendell, a strategist at RBC.
"The market is so sceptical of fiscal tricks that the Poles could end up shooting themselves in the foot."
SCRAMBLE
Tusk's centre-right government is scrambling to prevent public debt from breaching a ceiling of 55 percent of annual output, which would trigger spending cuts and hit a region-leading growth path that has been helped by public spending.
The senior government source said Warsaw should seek savings in other areas -- for example by cutting special military pensions and streamlining public fund management -- but not all cabinet members agreed more decisive steps were urgent.
Officials have said Finance Minister Jacek Rostowski and the economic council advising Tusk originally sought an even lower level of cash transfers, possibly only slightly above 2 percent.
Poles pay 12 percent of salaries into an inefficient state pension system and an obligatory 7.3 percent more to private funds, the main players on the Warsaw stock and bond markets with portfolios worth about 200 billion zlotys ($64.98 billion).
Warsaw hopes to get the EU's approval to deduct the bonds meant to replace the cash from its overall debt calculation and hopes to have a solution agreed before the middle of December, but Brussels' approval is far from clear.
On Tuesday, a diplomatic source said the Commission could persist with disciplinary action over Hungary's budget if it saw its pension move insufficient to cut the deficit sustainably.
Warsaw has repeatedly criticised Hungary's decision, saying predictability of pension systems was crucial to the stability and credibility of countries on the markets.
The state-supported system contributes around 26 billion zlotys annually to pension funds and reducing the amount of cash funds would cut what funds have to invest in both equities and potentially ordinary government bonds.
"Polish bonds are loosening, and this is already part of the markets expressing concern over these proposals," Marek Wichelmi, spokesman for a lobby group that encompasses 12 of Poland's 14 private pension funds. (Writing by Michael Winfrey; Editing by Patrick Graham)