SINGAPORE/BEIJING, Jan 17 (Reuters) - London copper prices
crept forward for a third straight session on Thursday as
China's move to inject liquidity into the financial system
boosted expectations of higher demand in the world's top
industrial metals consumer. 
    The People's Bank of China is injecting 250 billion yuan 
($37 billion) through seven-day reverse bond repurchase
agreements and 150 billion yuan through 28-day reverse repos,
traders said.
    Shanghai copper has flipped into backwardation amid a
promise of value-added tax (VAT) cuts in China, which has
increased near-term demand for physical copper, brokerage Jinrui
Futures said in a note.
    The tax reductions are not expected to be formalised until
March but Jinrui Futures said their implementation could result
in a 400 yuan a tonne boost to the ShFE copper price for every
percentage point VAT decrease.
    Prices at the close showed a 10 yuan a tonne backwardation
between the March and April ShFE copper contracts and a 120 yuan
a tonne backwardation from April to May.
    * COPPER: Three-month copper on the London Metal Exchange
 was up 0.2 percent at $5,979 a tonne, as of 0709 GMT,
while the most-traded March contract on the Shanghai Futures
Exchange closed 0.5 percent firmer at 47,380 yuan
($7,003.28) a tonne.
    * ZINC: The metal used to galvanise steel rose as much as
1.8 percent in Shanghai to 20,960 yuan a tonne, its
highest since Dec. 12 before closing at 20,885 yuan, while LME
zinc was up 0.1 percent to $2,500 a tonne after touching
a one-week high. 
    "Spec positioning is largely flat now on our estimates on
both LME and ShFE" zinc, Marex Spectron said in a note.
    * ALUMINIUM: Aluminium led the rest of the LME
complex lower, falling 0.6 percent to $1,849.50 a tonne after
the U.S. Senate on Wednesday rejected legislation to keep
sanctions on companies linked to Russian oligarch Oleg
Deripaska, including aluminium firm Rusal.  
    * ALCOA: Top U.S. aluminum producer Alcoa Corp beat
Wall Street estimates for quarterly profit on Wednesday, buoyed
by strength in its alumina segment, but shares slipped after the
company did not provide a closely watched profit measure for the
full year.