* Investors look to Trump speech for clarity on economic policy
* Metals markets looking for big U.S. infrastructure spend
* Supply stoppages at major copper mines support copper prices
* Deutsche Bank ups aluminium forecasts for 2017, 2018 by 7.5 pct (Updates with official prices, adds quotes on aluminium)
By Eric Onstad
LONDON, Feb 28 (Reuters) - Zinc and copper prices edged up on Tuesday as ongoing strikes in Canada and Chile added to supply worries, but gains were capped by uncertainty ahead of a key speech by U.S. President Donald Trump.
Benchmark zinc on the London Metal Exchange was bid up 0.4 percent at $2,817 a tonne after failing to trade in official open outcry trading, while copper was bid 0.1 percent firmer at $5,939.50.
"Zinc and copper are pretty well supported by supply problems but there's no real urge to move higher. The market is waiting for Trump's address tonight," said Robin Bhar, head of metals research at Societe Generale.
"To take us on the next leg up and to get more speculators and investors buying into this commodity reflation, we need to flesh it out with more concrete information. We're running up against some producer selling and spec profit taking at the highs."
A strike continued at Noranda Income Fund's zinc processing plant in Quebec, the second-largest in North America.
Zinc prices have nearly doubled over the past 13 months, but signs of tightening in the global market for refined zinc means the rally may have further to run.
Investors, however, are cautious ahead of Trump's speech at a joint session of U.S. Congress at 9 p.m. (0200 GMT Wednesday).
World stocks hovered just off all-time highs after Trump met U.S. state governors at the White House on Monday and said he sees "big" infrastructure spending.
Losses in copper were shallow due to persistent concerns over supply from large mines in Chile and Indonesia.
A strike at the Escondida copper mine in Chile, the world's largest, appeared far from ending on Monday as the conflict neared its third week.
Elsewhere, shareholders are pressuring miner Freeport-McMoRan Inc to stand up to the Indonesian government over changes the Southeast Asian country wants to make in the U.S. miner's contract, with output halted at a giant copper mine.
"Copper was stronger for most of the day, which opened things up for profit-taking, which knocked prices back," said a trader in Perth, Australia.
Aluminium was bid down 0.3 percent at $1,895 a tonne
Deutsche Bank increased their aluminium price forecasts for this year and next by an average of 7.5 percent, a note said.
"Chinese 'supply side reforms' or 'de-capacity' and a much more stringent focus on environmental standards could hold the key to a much healthier market," analyst Grant Sporre said.
"Although the supply demand fundamentals for the aluminium market have improved significantly since the beginning of 2016, we think the current spot price is at risk of a correction."
Nickel was bid down 1 percent to $10,940, lead was bid 0.8 percent firmer at $2,273 and tin traded up 1.2 percent to $19,175 in official rings.
Three month LME copper
Most active She copper
Three month LME aluminium
Most active She aluminium
Three month LME zinc
Most active She zinc
Three month LME lead
Most active She lead
Three month LME nickel
Most active She nickel
Three month LME tin
Most active She tin
Additional reporting by James Regan in Sydney, editing by David Evans/Keith Weir