(Adds detail, updates prices) MELBOURNE, March 23 (Reuters) - Base metals in Shanghai and London fell on Friday on fears that an escalating trade spat between China and the United States, the world's top two economies, could derail global growth and damage demand. China urged the United States on Friday to "pull back from the brink" as U.S. President Donald Trump's plans for tariffs on up to $60 billion in Chinese goods brought the world's two largest economies closer to a trade war. In London, copper and aluminum hit the weakest since mid- December, while in Shanghai, copper prices retreated towards levels not seen since mid-2017, although prices cut losses towards the end of the Asian day. However, seasonally building inventories and deteriorating chart signals pointed to more downside in the near term. "It's hardly surprisingly the metals markets reacted with a huge sell-off as speculators and funds exited the markets with the falls being accelerated in many cases by the activity of HFT (high frequency trading) algorithms and trading volumes ballooned in the rush to get out," said brokerage Kingdom Futures. "As if the markets did not have enough, there are U.S. durable goods numbers out along with home sales data, which could yet throw the markets into further confusion," it said in a report.
* COPPER: London Metal Exchange copper was down 0.2 percent at $6,679.50 a tonne, as of 0724 GMT, having plumbed its weakest since mid-December. Prices extended a 1.4 percent fall from the previous session, breaking the 200-day moving average for the first time in around 18 months.
* Shanghai Futures Exchange copper tumbled 1.7 percent to 50,110 yuan ($7,923) a tonne, having struck the weakest since July 2017.
* TRUMP: U.S. President Donald Trump signed a presidential memorandum on Thursday that could impose tariffs on up to $60 billion of imports from China.
* CHINA: China's commerce ministry said on Friday that the country was planning measures against up to $3 billion of U.S. imports to balance U.S. tariffs against Chinese steel and aluminum.
* STEEL: A sell-off in steel spilled into inputs nickel and zinc. Shanghai rebar tumbled near 7 percent, while Shfe nickel slid 3 percent. LME nickel fell 0.9 percent, adding to the 2 percent loss from the previous session.
* ALUMINIUM: Shfe aluminum sank to its weakest since October 2016, hammered by concerns of rising China supply now pollution-linked output curbs have expired as well as U.S. trade tensions. LME aluminum held at three-month lows, having broken below the 200DMA mid-month.
* SCRAP: China's waste plastic imports dried up almost entirely in February and scrap metal imports fell by 38.5 percent year on year as the country enforced its clampdown on foreign waste, customs data showed on Friday.
BASE METALS PRICES 0723 gmt Three month LME copper 6685 Most active ShFE copper 50110 Three month LME aluminum 2068.5 Most active ShFE aluminum 13755 Three month LME zinc 3210 Most active ShFE zinc 24665 Three month LME lead 2351.5 Most active ShFE lead 18435 Three month LME nickel 13070 Most active ShFE nickel 98520 Three month LME tin 20705 Most active ShFE tin 141500
BASE METALS ARBITRAGE
LME/SHFE COPPER LMESHFCUc3 877.28 LME/SHFE ALUMINIUM LMESHFALc3 -1422.89 LME/SHFE ZINC LMESHFZNc3 551.36 LME/SHFE LEAD LMESHFPBc3 323.19 LME/SHFE NICKEL LMESHFNIc3 527.78
($1 = 6.3250 Chinese yuan)
(Reporting by Melanie Burton, Editing by Sherry Jacob-Phillips and Subhranshu Sahu)