* LME/ShFE arb: bit.ly/2wZSAEz
* GRAPHIC-2018 asset returns: tmsnrt.rs/2jvdmXl (Updates with closing prices)
By Jan Harvey
LONDON, May 30 (Reuters) - Copper fell to a three-week low on Wednesday as jitters over the U.S.-China trade stand-off kept up pressure on cyclical assets like industrial metals, already hurt this week by worries over political turmoil in Italy.
The metal clawed back some lost ground as easing concerns over Italy's political crisis led stock markets higher, but remained in negative territory.
China warned on Wednesday it was ready to fight back if Washington was looking for a trade war. That came after the United States, in a change of tone, said it still held the threat of imposing tariffs on $50 billion of imports from China.
Given those pressures, copper is sliding towards the bottom of its recent range, Saxo Bank's head of commodity strategy Ole Hansen said.
"The U.S.-China trade spat seems to be hotting up again after yesterday's announcement from the White House," Hansen said. "The global growth and demand outlook does not need a new political/financial crisis in Europe and a potential trade war between the world's two biggest economies."
* COPPER PRICES: Three-month copper on the London Metal Exchange ended the day down 0.3 percent at $6,839 a tonne, having earlier touched its weakest since May 8 at $6,727.
* COPPER INVENTORIES: On-warrant copper stocks in London Metal Exchange warehouses MCUSTX-TOTAL - representing metal not earmarked for delivery - eased to 191,200 tonnes, data showed on Wednesday. That was the lowest since January.
* INDIA SMELTER: Vedanta Resources is working on a legal challenge to an Indian state's closure of one of its copper smelters but will not proceed until tensions have eased over the deaths of 13 people during protests last week.
* U.S. GROWTH: U.S. economic growth slowed slightly more than initially thought in the first quarter, but a robust labour market and income tax cuts are likely to boost activity this year.
* ZINC STOCKS: On-warrant zinc stocks in LME warehouses eased to 195,225 tonnes, their lowest in a month. The proportion of cancelled warrants - metal earmarked for delivery and therefore not available to the market - rose to nearly 15 percent from 6 percent last week.
* ZINC PRICES: LME zinc closed up 1.3 percent at $3,130 a tonne, off an earlier one-month high of $3,139.50.
* ALUMINIUM PRICES: LME aluminium finished 0.2 percent lower at $2,270 a tonne.
* OTHER METALS: LME lead ended 0.4 percent lower at $2,435 a tonne, while tin finished up 0.7 percent at $20,575. Nickel closed at $15,135 a tonne, up 1.5 percent.
Additional reporting by Manolo Serapio Jr. in Manila Editing by Susan Fenton and David Holmes