MELBOURNE, March 7 (Reuters) - London metals slipped on Wednesday on heightened fears of a trade war that could derail global growth after U.S. President Donald Trump said he would push ahead with his plan to impose heavy tariffs on steel and aluminium imports. FUNDAMENTALS: * London Metal Exchange copper slipped by 0.5 percent to $6,971 a tonne by 0223 GMT, paring a 1.4 percent gain from the previous session. Prices have traded in a $6,850-$7,250 range since mid-February, bumping up against four-year highs, as global manufacturing has ramped up to feed construction and power industries in Europe, China and the United States. * Shanghai Futures Exchange copper edged up by 0.3 percent to 52,530 yuan ($8,302) a tonne. * U.S. ECONOMY: Economic nationalists appeared to gain the upper hand in a White House battle over trade with the resignation of Donald Trump's top economic adviser, Gary Cohn, on Tuesday in a move that could ramp up protectionist measures and risk igniting a global trade war. * COPPER: "A softer dollar brought copper up above $7,000 last night but I think fear is on again," said a trader in Singapore. * DOLLAR: The dollar extended its latest retreat on Wednesday after Gary Cohn announced his resignation. * CHINA ECONOMY: China is fully confident of its ability to fend off systemic debt risks while authorities expect no significant changes in government debt ratio in the coming years, finance minister Xiao Jie said on Wednesday. * ZINC: Brazilian miner Nexa Resources expects demand for zinc to outpace supply, keeping prices for the metal at $3,400 to $3,500 a ton for the rest of the year, Chief Executive Tito Martins said on Tuesday. * Premiums for zinc in Shanghai bond have sunk to the weakest since May last year at $145-170, latest data shows, after exchange stocks in the U.S. surged this week, soothing supply concerns. * U.S. ECONOMY: New orders for U.S.-made goods recorded their biggest decline in six months in January and business spending on equipment appeared to be slowing after strong growth in 2017. * ALUMINA: A Brazilian court denied a request by Norwegian aluminium maker Norsk Hydro ASA to resume full operations at its unit Hydro Alunorte, the court said in a statement, in the latest setback after allegations it had contaminated water in the area.