* TSX closes down 0.5 percent at 12,040.01
* Nine out of 10 main sectors end lower
* Resource issues lead retreat (Adds details, quotes)
By Claire Sibonney
TORONTO, March 18 (Reuters) - Toronto's main stock index closed moderately lower on Thursday as concerns about tighter credit in China and doubts about an aid plan for debt-stricken Greece increased investor caution over the global economic outlook and pressured commodity prices.
Both oil and natural gas prices weakened, sending the TSX's energy group down 0.9 percent. April crude fell 0,88 percent to $82.20 a barrel, while gas futures hit multi-month lows after a U.S. government report showed an unexpectedly light weekly inventory draw.
"It seems like a very measured sort of decline," said Elvis Picardo, an analyst and strategist at Global Securities in Vancouver.
"There's absolutely no sense of panic. It's comforting to see the TSX is still managing to hold above the 12,000 mark," he added. The index touched a 17-month high of 12,122.47 on Wednesday.
The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE closed down 60.65 points, or 0.5 percent, at 12,040.01, with nine out of its 10 sectors finishing lower. Technology stocks were slightly higher.
Gold miners fell despite flight-to-quality buying of bullion. Barrick Gold Corp (ABX.TO), the world's biggest producer, dropped 0.6 percent to C$40.32, while Goldcorp Inc (G.TO) fell 1.1 percent to C$39.82.
"The thing with gold is that price of gold in U.S. terms has been holding up quite all right, but in Canadian dollar terms gold prices have been slightly weak, and that's again purely because of the appreciation of the Canadian dollar," Picardo said.
The Canadian dollar fell back on Thursday after hitting a near 20-month high the day before, but continued to stalk the 99 U.S. cent mark. [CAD/]
Concern over China arose as its central bank was set to mop up a massive 213 billion yuan ($31 billion) in liquidity in open market operations this week, which could cap demand for commodities. [ID:nTOE62H02T]
Worries about Greece's fiscal outlook also weighed on markets. A report on Thursday quoting a Greek official saying the country was not optimistic about aid from euro zone members, which further supported the safe haven attraction of the U.S. dollar, which also tends to weigh on commodity prices. [ID:nLDE62H0LL]
As well, base metal prices were depressed, pressuring miners Teck Resources TCKb.TO, down 1.7 percent at C$41.26 and Ivanhoe Mines (IVN.TO), which fell 1.6 percent at C$16.42.
The TSX index settled lower after flip-flopping in early trade, and was expected to show little momentum one way or another in coming days.
"At this point in the game I think what we need is a new catalyst to push the markets higher and it's quite likely that we'll be trading sideways until that happens," said Picardo.
"I think that will probably happen sometime next month when you begin to see the earnings reports start to come out."
Fergal Smith, managing market strategist at Action Economics, said the risks of a market retreat remain.
"For us, we're kind of looking for the TSX to maybe stretch higher and test trendline resistance off the September, December, January highs at 12,199. But, you know, we're wary that there's risk of a sharp bearish reversal from there."
$1=$1.01 Canadian Reporting by Claire Sibonney, editing by Rob Wilson