LONDON, Dec 12 (Reuters) – Copper slipped on Wednesday as investors shrugged off upbeat comments from U.S. President Donald Trump about a potential trade deal with China, while the dollar hovered near a one-month peak against its peers. Trump said he would intervene in the Justice Department’s case against a top executive at China’s Huawei Technologies if doing so would help close a trade deal. “Even when you get a glimmer of good news it can easily be reversed by a tweet. Until a trade deal is signed, markets are going to be ‘glass half empty’. Also some economic data is beginning to look a bit tired,” said William Adams, head of research at Fastmarkets. “That said, underlying (supply) fundamentals for copper are strong and going to improve next year,” he added. The dollar steadied near a month high, with the Federal Reserve widely expected to raise interest rates at its upcoming meeting. U.S. rates may be nearing a peak, but relative rate differentials still offer some support for the dollar. A stronger dollar makes dollar-priced metals more expensive to import for countries using other currencies.

* COPPER: Three-month copper on the London Metal Exchange (LME) traded down 0.4 percent at $6,143 a tonne in official midday rings, heading for falls of around 15 percent this year despite decade-low stocks at LME warehouses.

* COPPER SHORT POSITIONS: Copper is showing a marginal net speculative short or sell position of 1.2 percent of open interest, according to estimates from broker Marex Spectron.

* STEEL: Chinese steel prices ended three days of losses to edge higher, with top steelmaking city Tangshan planning further production cuts this month as it races to meet its air quality target this year.

* ALUMINIUM: For a column on U.S. tariffs failing to dent Chinese aluminium export surge, click:

* ALUMINIUM OUTPUT: “U.S. production is expected to climb 67 percent this year, as new aluminium expansion projects come online … adding to a globally oversupplied market,” said SP Angel in a note, quoting the Economic Policy Institute think tank.

* LEAD: Fitch revised down its LME lead forecast for 2019 to $2,350 a tonne from $2,450 as prices have underperformed in the second half, with long-term prices to fall on weaker global demand and surpluses.

* METALS PRICES: Aluminium traded down 0.2 percent in rings at $1,936 a tonne, steelmaking raw material zinc traded flat at $2,590, lead traded flat at $1,975, tin traded up 0.4 percent at $19,200. Stainless steelmaking ingredient nickel traded 0.1 percent higher at $10,780 a tonne.