(Adds detail on Commission report)
FRANKFURT, May 7 (Reuters) - The European Central Bank said on Wednesday it has "considerable concerns" about whether Slovakia can keep inflation under control in the longer term if it adopts the euro in January as the country plans.
At face value, Slovakia met the euro entry tests on inflation, public finances, currency stability and interest rates when the snapshot of its economy was taken in March.
But in its latest convergence report, the ECB queried whether Slovakia can avoid higher inflation if it does join the single currency region, saying there were upside price risks.
"To sum up, although the 12-month average rate of ... inflation in Slovakia is currently well below the reference value, there are considerable concerns regarding the sustainability of inflation convergence," the ECB said in a report on EU countries' readiness to join the euro.
The ECB does not make a formal recommendation on whether countries should be allowed to adopt the euro or not. A separate report prepared by the European Commission on Wednesday proposed Slovakia be allowed to adopt the euro in 2009.
The Commission's recommendation has to be backed by European Union finance ministers and then approved by political leaders, a decision expected in June.
Most economists expect a positive verdict for the central European country, which would then become the 16th country to formally adopt the euro and join on Jan. 1 next year.
The ECB said Slovakia also needs to cut its budget deficit faster, tackle a gummed-up labour market and keep a lid on wage rises if it is to avoid excessive inflation when it is no longer able to set its own interest rates or revalue its currency.
The ECB report showed that, as expected, Slovakia currently met the formal criteria on joining the single currency, with moderate inflation, low public debt, a shrinking budget deficit, fairly stable currency and low long-term interest rates.
INFLATION A WORRY
But the ECB -- whose main goal is to keep euro zone inflation just below 2 percent -- has been stung by a sharp rise in inflation in Slovenia, the only other ex-Communist state to join the euro zone.
Though Slovenia met the entry criteria before it joined in 2007, its inflation is now the highest in the euro zone at 6.2 percent in April.
Slovak inflation hit 3.6 percent in March but the average over the previous year, which is used to assess eligibility, was 2.2 percent, well below the 3.2 percent maxiumum allowed.
The ECB nonetheless said it was concerned that Slovak inflation had been kept down partly by the appreciation of the Slovak crown <EURSKK=>, which will no longer be possible if Slovakia adopts the euro.
The ECB noted estimates that the dampening effect of currency appreciation may have been as high as 1 percentage point in 2007, although the Slovak central bank estimated the impact at 0.3-0.5 percentage points.
"Looking ahead, the latest available inflation forecasts from major international institutions ... suggest that annual average inflation is likely to rise considerably in 2008 and decrease slightly in 2009," the ECB said.
"In view of current developments in global energy and food markets, and given ongoing strong growth in domestic demand, as well as the tightening of labour market conditions, the balance of risks to these forecasts for Slovakia is on the upside."
Slovak central bank governor Ivan Sramko -- who will join the ECB's Governing Council if his country adopts the euro -- disputes the idea that the strength of the crown had played a major role in controlling Slovak inflation.
"The fulfilment of the inflation criterion is no one-day wonder, but the expression of a sustainable development," he told Germany's Frankfurter Allgemeine Zeitung in an interview published ahead of the report on Wednesday. (Reporting by David Milliken and Krista Hughes; editing by Stephen Nisbet)