* Falling govt debt levels seen hurting liquidity
* Lower issuance to push down Swedish yields
* Debt Office eyes fewer auctions, focus on 5-, 10-yr debt
By Simon Johnson
STOCKHOLM, March 23 (Reuters) - Sweden may come to face a problem for which some debt-ridden euro zone states would gladly swap their own woes - a consequence of serious debt-cutting.
The worry for some professionals in Sweden's debt market is that steadily reducing supply could shrink liquidity to the point where the market can no longer function effectively.
Finance Minister Anders Borg, representing a government intent on cutting its debt burden further, dismisses such concerns, saying "no country in the world has had a problem with too low debt".
However, some warn that driving Sweden's debt down too far could deprive pension funds and banks of safe, long-term debt paper, as well as dislocating a fund-raising mechanism the country might need to tap again in some future crisis.
"If you pay off on the debt and make the outstanding volumes less and less, you will have problems in the market," said Olof Manner, Head of Scandinavian Rates Sales at RBS.
Sweden's Debt Office reckons debt will hit 1 trillion crowns ($158 billion) by the end of 2013 -- below 30 percent of GDP -- from about 1.2 trillion at the end of 2010.
By contrast, crisis-hit Ireland's debt will be around 110 percent of GDP at the end of 2013.
The Nordic state has bounced back strongly from its 2009 recession. Gross domestic product rose 5.5 percent last year and an output rise of more than 4 percent is expected for 2011.
Such fundamentals have encouraged investors, leading to the spread of Swedish 10-year paper over equivalent German debt to narrow to about 10 basis points from 34 basis points at the start of the year.
But to keep investors happy, Sweden's market for its state debt needs to be kept liquid even as the state is busy paying back its borrowings.
As Debt Office debt management head Thomas Olofsson recently told Reuters, the first thing investors ask is how easy it is to sell the securities after they have bought them.
Liquid bond markets are also key for the smooth functioning of the financial system.
The yield curve from government bonds provides a pricing benchmark. Banks also need high-quality debt as a capital buffer with new, tougher rules likely to amplify this need. Pension funds use long-term paper to match liabilities.
The state might also have to borrow in a hurry, as it did in the global crisis.
"We must be prepared to borrow a lot in a crisis and then it is important to have low debt, but it is also important to have an investor base and infrastructure," Olofsson said.
"If we continue to have large surpluses in the coming years, sooner or later we would reach the point where liquidity would be more difficult to support," he added.
Olofsson gave the example of Denmark, where central government debt fell to 11 percent of output by the end of 2008, but doubled back to 22 percent of gross domestic product (GDP) in 2010 after the financial crisis ravaged its banks.
Even in the fiscally strong years, the central bank, which runs debt management for Denmark, chose to keep a functioning debt market due to the costs of having to restart one from scratch.
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For graphics on Nordic states' maturity profiles: http://r.reuters.com/wuz97r
Swedish bond spread http://r.reuters.com/rec68r
Sweden's falling debt levels http://r.reuters.com/wec68r ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
YIELDS TO GO LOWER
Analysts have calculated that were Sweden to continue paying down its debt at the same rate as in the past 15 years, it would be debt-free sometime in the 2020s.
Should rating agencies downgrade more debt-laden euro zone countries like Spain and Portugal, global investors are likely to boost holdings of Swedish debt, further stretching supply.
In the short term, this will make it cheaper for the government to borrow.
"We think Swedish long-term yields could go a little bit below German ... in the next 1-2 years," Knut Hallberg, analyst at Swedbank said. "The main reason for that is lack of supply."
Rating agency Moody's also views the trend as positive, with Dietmar Hornung, Senior Credit Officer at Moody's Sovereign Risk Group, saying falling levels of borrowing were good from a creditworthiness point of view.
Swedbank's Hallberg said outstanding debt needs to be more than 800 billion crowns ($125.9 billion) for a liquid market.
Debt Office head Bo Lundgren put the figure at 700-800 billion crowns with at least 50-60 billion outstanding in benchmark issues.
It will take some time to reach that level -- and that's if demographic changes don't push budgets back into deficit soon.
The Debt Office, which will hand the government a report on the falling debt in late September, is unlikely to sit still.
Its options include withdrawing or cutting back on some parts of the debt market in order to focus on more liquid instruments.
For instance, it could reduce T-bill issuance further, cut foreign currency borrowing or borrow on behalf of a wider client base, such as local authorities.
Increasing buybacks would also give room for new borrowing.
T-Bill issuance is already expected to fall, as is foreign borrowing, and the Debt Office has said it will focus issuance on 5- and 10-year debt and probably hold fewer auctions ahead.
Lundgren also told Reuters that debt levels of 30 percent of GDP meant the government had flexibility to consider whether to continue to pay off debt, or use the money for public investment projects, though he stressed that was a political decision. (Editing by Stephen Nisbet)