* Q2 earnings growth weak, in line with expectations
* Loan-loss provisions up almost 15-fold
* State bank seen as proxy for slowing Russian economy
* Sberbank sees 2013 profit at lower end of guidance
By Katya Golubkova and Oksana Kobzeva
MOSCOW, Aug 28 (Reuters) - Russia's largest bank, Sberbank , trimmed its estimate for full-year net profit on Wednesday to 370 billion roubles ($11.2 billion), at the lower end of a previous forecast range, after higher bad loan provisions weighed on quarterly results.
Russian banks have piled into high-margin consumer lending as demand for credit slowed at companies.
However, new central bank rules require lenders to set aside more money to cover risks on high-interest loans, potentially weakening their capital position, while a slowing economy has raised fears that consumers will struggle to repay their debts.
"Our net profit will be close to the lower end of our forecast," Chief Executive German Gref told a conference call, stopping short of formally revising an earnings guidance range of 370-390 billion roubles.
The former Soviet state savings bank said it set aside 30.9 billion roubles against potential bad loans in the second quarter - nearly 15 times higher than the year-earlier figure of 2.1 billion roubles.
Analysts had expected the bank to set aside 30.2 billion.
The Economy Ministry cut its 2013 economic growth forecast on Monday to 1.8 percent from 2.4 percent, blaming weaker exports and consumption.
State-controlled Sberbank accounts for 29 percent of Russia's total banking assets and holds 46 percent of household deposits, making it a bellwether for the country's $2 trillion economy.
Gref, a former Russian economy minister, told analysts on a conference call that the first half of the year had been more difficult than expected, but he forecast a slight improvement in the economy in the third and fourth quarters of the year.
His full-year earnings forecast implied a 6 percent increase on 2012.
PROFIT IN LINE
Second-quarter net profit grew by 3.5 percent year on year to 86 billion roubles, broadly in line with an average analyst forecast of 85.8 billion roubles.
Analysts said Sberbank's resilient interest margin helped offset the hit from provisions.
Andrei Klapko, a banking analyst at Gazprombank in Moscow, estimated tjat Sberbank's net interest margin narrowed by just 10 basis points in the second quarter to 5.9 percent, close to the bank's lower end full-year forecast, now set at 5.9-6.1 percent.
Shares in Sberbank - which are widely held and actively traded - were down 0.7 percent at 1414 GMT, a little weaker than Russia's blue-chip MICEX index.
Smaller rival Vozrozhdenie on Tuesday reported a 72 percent drop in second-quarter earnings due to high provisions and weak net interest income as lending is slowing.
Sberbank expanded its retail loan book, before provisioning, by 10.9 percent in the first half of the year while its corporate lending grew by just 4.2 percent.
Its non-performing loan ratio was 3.2 percent, unchanged from the end of 2012. Its Tier 1 capital adequacy ratio - a measure of the ability to absorb losses - fell to 10.5 percent from 10.9 percent at the end of the first quarter.
In a presentation to analysts, Sberbank raised its forecast of the so-called cost of risk - or the reserves it would have to set aside this year to cover lending risks - to 1.1 percent of its credit portfolio from 0.75-0.8 percent previously.