* Trump-Putin summit could bring Rusal sanctions relief
* U.S. and China trade tensions knock copper (Adds closing prices)
LONDON, July 13 (Reuters) - Copper clocked up a fifth weekly loss on Friday as trade tensions between the United States and China rumbled on, while aluminum hit a three-month low ahead of a summit between U.S. President Donald Trump and Russian President Vladimir Putin.
Trump and Putin are due to meet in Helsinki on Monday and aluminum investors are looking for any hint that U.S. sanctions on Rusal, the world's second-biggest aluminum producer, will be eased or lifted.
"There's an expectation that if you're going to see the sanctions removed from Rusal it may come out of the meeting (between Trump and Putin)," Nick Snowdon, metals strategist at Deutsche Bank, said.
On the trade dispute between the United States and China, he said speculative investors in copper were neutrally positioned, reflecting a cautious attitude amid economic uncertainty.
"In copper you had probably the single largest (long) position ever liquidated (on the Shanghai Futures Exchange) in June. That's done and dusted, so that (trade) uncertainty (now) lends itself to investors staying on the sidelines and prices stabilizing."
COPPER: Three-month copper on the London Metal Exchange closed up 0.2 percent at $6,238 a tonne, but was down 1 percent for the week. The metal has fallen some 15 percent in five weeks of losses.
ALUMINIUM: Aluminium closed down 0.5 percent at $2,031 a tonne, having hit its lowest since early April at $2,021.50.
ALUMINIUM TECHNICALS: Indicating nearby tightness, cash aluminum traded at a premium of $49.50 a tonne to the three-month price, its highest level since early April. <CMAL0-3> For a column on aluminum click:
CHINA TRADE SURPLUS: China's trade surplus with the United States swelled to a record in June, a result that could further inflame a bitter trade dispute with Washington.
CHINA METALS EXPORTS: China's aluminum exports exceeded half a million tonnes for the second time ever in June, while steel exports hit an 11-month high, defying U.S. tariffs.
CHINA GROWTH: Analysts have raised their 2018 growth forecasts for China's economy, a surprising result given an escalating trade war with the United States.
FREEPORT: Copper prices are being pressured by concern about rising supply after Indonesia on Thursday struck an agreement with Freeport-McMoRan Inc and Rio Tinto to buy a controlling stake in the world's second-biggest copper mine, Grasberg.
OTHER METALS: Zinc closed down 0.1 percent at $2,578, lead ended down 0.6 percent at $2,202, tin closed up 0.8 percent at $19,795 while nickel ended down 1.6 percent at $13,970.
(Additional reporting by Naveen Thukral, editing by Jane Merriman and David Evans)