* Gold-platinum ratio at tightest since April 2012
* Coming up: ECB rate decision, 1245 GMT (Changes dateline, byline, adds quotes, update prices)
By Veronica Brown
LONDON, Jan 10 (Reuters) - White metals stole a march on bullion on Thursday, with gains in platinum and palladium outpacing those of gold as data pointed to an improved economic backdrop in China.
Spot platinum hit a three-week high, while palladium was on course for a third day of gains - in stark contrast to gold, which struggled to rally from a recent 4-1/2 month low at $1,625.79.
By 1117 GMT, platinum was up 0.8 percent at $1,606.50 per ounce, while palladium had surged 1.8 percent to $695.90. Gold held a firmer tone, rising 0.2 percent to $1,661.54.
With gold and platinum's recent moves in different directions, the differential between the two narrowed to its tightest since April 2012.
China's export growth rebounded more strongly than expected in December from a three-month low, expanding at the fastest rate in seven months, data showed on Thursday. The outlook for 2013 remained cloudy, however, with U.S. and European demand for Chinese goods still subdued.
Signs of continuous improvement in U.S. auto sales have also given a brighter tone to platinum group metals, alongside supply issues created by labour unrest in South Africa's producing belt.
"The overall (Chinese) trade data is looking positive in terms of exports. For PGMs there's some positivity, surprisingly, on the auto sector," Citigroup analyst David Wilson said.
Gold rose but was hemmed into tight ranges as investors waited for a decision on European Central Bank monetary policy.
The ECB is expected to leave borrowing costs unchanged, but economists have mixed views on the chances of a rate cut in the next few months due to a murky economic outlook.
Central bank monetary stimulus was a key driver behind gold's 12th year of annual gains in 2012 as investors were drawn to bullion as a hedge against inflation.
Gold has been moving in a narrow range of about $25 this week, with the upside capped by hints that open-ended U.S. bond buying may be nearing its limit.
Gold hit a more than four-month low after minutes from the U.S. Federal Reserve's last meeting showed officials were concerned about the side effects of its bond-buying programme.
"The market got a little concerned about how aggressive the Fed will be," said Jeremy Friesen, commodity strategist at Societe Generale in Hong Kong, adding that the market was expected to rebound.
SocGen expected gold to average $1,700 an ounce in the first quarter of the year as well as for all of 2013.
Robust purchases on the physical bullion market in Asia were showing signs of slowing down after prices settled in a range, dealers said.
"Prices have been at the current level for a week or so, and we will see some slowdown in physical buying, unless prices go down to $1,640 or $1,650," said a Singapore-based trader. (Additonal reporting by Rujun Shen in Singapore; Editing by Jane Baird)