Aug 12 (Reuters) - Copper prices declined on Wednesday on rising uncertainty about additional U.S. fiscal stimulus to help boost a pandemic-ravaged economy and as the dollar strengthened, making the metal more expensive for holders of other currencies.

Three-month copper on the London Metal Exchange fell 0.6% to $6,345.50 a tonne by 0743 GMT, while the most-traded September copper contract on the Shanghai Futures Exchange declined 1.7% to 49,870 yuan ($7,175.95) a tonne.

A stalemate between the Republican White House and congressional Democrats over coronavirus relief ended in a fourth day without talks on Tuesday, with each party blaming the other for intransigence.

Against a basket of currencies, the dollar extended a bounce made last Friday as U.S.-China tensions ratcheted higher with President Donald Trump's ban on TikTok and WeChat.

Simmering tensions between Washington and Beijing also pressured prices of copper as investors feared economic retaliation that could further dampen sentiment and a global economic recovery.

"Investors are perhaps in a wait-and-see mode, awaiting further economic stimulus and to see how U.S.-China trade talks go before putting on further bullish bets," ING analysts said in a note.

FUNDAMENTALS

* Rapidly rising stainless steel production in top consumer China has helped to preserve demand and prices of key ingredient nickel, but analysts still expect a supply overhang of the metal valued for its anti-corrosive properties.

* The China Nonferrous Metals Industry Association's CMRA recycling branch urged shippers to continue carrying copper and aluminium scrap, citing concern over potential raw material shortages.

* Indonesia's July refined tin exports in July rose 10.2% year-on-year to 4,845.24 tonnes.

* LME nickel declined 1.4% to $14,150 a tonne and lead was down 0.4% to $1,953 a tonne. In Shanghai, tin dropped 1.1% to 143,540 yuan a tonne and nickel fell 1% to 112,300 yuan a tonne.

* For the top stories in metals and other news, click or ($1 = 6.9496 yuan) (Reporting by Mai Nguyen; Editing by Sherry Jacob-Phillips, Aditya Soni)