(Adds quotes from statistics office, more analysts' comments) By Peter Laca BRATISLAVA, Dec 7 (Reuters) - The Slovak economy grew by a record 9.8 percent in the third quarter, data showed on Thursday, and analysts said the fast expansion may bring another interest rate hike in the coming months. Confirming a flash estimate last month, the Statistics Office said the jump in gross domestic product growth was a one-off, but the new EU member's economy was likely to continue expanding well above the bloc's average in the coming quarters, buoyed by big investments such as new car factories. "This jump was caused by combined effects from large companies that had been preparing the start of production for the fourth quarter," Pavol Balaz, head of the Statistics Office's National Accounts Department, told reporters. The Office revised its full-year GDP forecast to 7.7 percent growth, from 6.5 percent previously, and predicted 7.2 percent growth in the first three months of 2007. "The key drivers were investments, shown in inventories, and domestic demand," said Slovenska Sporitelna senior economist Maria Valachyova. "Inventories will transform into exports, and growth should remain strong in the future." Economic growth will boost state revenues and help leftist Prime Minister Robert Fico finance his social spending plans. Slovakia needs to cut its fiscal deficit next year to meet its goal of adopting the euro in 2009. Slovakia has had the highest growth rates among the four largest new EU members from central Europe over the past few years, and the third quarter figure brought it into the ranks of the world's fastest growing economies. Growth has been spurred by rising household consumption after years of belt-tightening reforms, but also by investment by companies such as French PSA Peugeot <PEUP.PA> and South Korean Kia Motors <000270.KS>. "The growth structure suggests the increasing potential of the economy, rather than its overheating," said ING Bank senior economist Lucia Steklacova. TRICKY RATE CALL The Slovak central bank (NBS) has raised the key two-week repo rate by 175 basis points this year to 4.75 percent because inflation risks from high energy costs and economic growth could endanger the euro adoption plan. But a crown <EURSKK=> rise by 5.7 percent in the past three months has limited retail price growth and allowed the NBS to keep rates on hold for the second month in a row in November. The crown firmed slightly after the GDP data, to 35.445 to the euro, matching its all-time highs, from 35.465. Slovenska Sporitelna's Valachyova said the GDP data did not point to an immediate need to raise rates again, but risks from strong demand and a possible crown correction could bring another 25 basis point hike. Other economists said the main rate has already peaked. "Although consumer demand accelerated a bit in the third quarter of 2006, the structure of economic growth makes us believe that an appreciating currency will be able to squeeze excessive demand-side inflationary pressures from the system," said Miroslav Plojhar, chief economist at Citibank Czech Republic. ((Reporting by Peter Laca; editing by Ruth Pitchford; Reuters Messaging: peter.laca.reuters.com@reuters.net; +421 2 5341 8402)) Keywords: SLOVAKIA ECONOMY/GROWTH