Nov 20 (Reuters) -Copper extended gains to a fourth session on Wednesday as the U.S. dollar weakened, while London aluminium held firm after China decided to remove export tax rebates.

Three-month copper on the London Metal Exchange (LME) CMCU3 rose 0.6% to $9,143.5 per metric ton by 0140 GMT, while the most-traded December copper contract on the Shanghai Futures Exchange (SHFE) SCFcv1 gained 0.8% to 74,600 yuan ($10,305.15) a ton.

The dollar pulled back after its recent blazing rally, making greenback-priced metals more affordable for other currency holders. USD/

LME aluminium CMAL3 climbed 0.5% to $2,657 a ton, rising for a second straight session.

China said on Friday it would cancel a 13% export tax refund for aluminium and copper products from Dec. 1. China's copper product exports are considerable, while the volume of aluminium exports is significantly higher.

"The reduction in export subsidies is probably also a measure to slow down the growth in smelting capacity, which has also continued to increase due to rising exports," Commerzbank said in a note.

"These measures are likely to support prices on the LME in the long term, as supply on markets outside China is threatening to become scarcer or more expensive."

LME nickel CMNI3 increased 0.4% to $15,930, zinc CMZN3 rose 0.6% to $2,969.5, lead CMPB3 was up 0.5% at $2,011 and tin CMSN3 advanced 1% to $29,160.

SHFE aluminium SAFcv1 rose 1.2% to 20,720 yuan a ton, nickel SNIcv1 rose 1.5% to 126,430 yuan, tin SSNcv1 added 0.2% to 242,580 yuan, lead SPBcv1 was up 0.4% at 16,850 yuan and zinc SZNcv1 added 0.9% at 24,905 yuan.

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Reporting by Ashitha Shivaprasad in Bengaluru; Editing by Subhranshu Sahu

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