Most industrial metals prices fell on Friday as uncertainty about trade talks and global growth outweighed Chinese plans to use government levers to underpin growth.

News of a tax cut for China's industrial sector sent zinc prices and spreads lurching in Shanghai.

Premier Li Keqiang promised broad policy steps to prevent a sharper slowdown for the world's second-biggest economy, the biggest consumer of base metals.

“I think that has helped to stabilise the sentiment and calm the market, but there is still some macro uncertainty lingering, so we're not seeing a massive rally in the metals prices,” said Xiao Fu, head of commodity market strategy at Bank of China International in London.

“Although the trade talks are progressing, we still don't know the outcome and there's some worry about the general weaker global GDP outlook.”

Benchmark aluminium on the London Metal Exchange fell into the red and traded down 0.7 per cent to $1,890 a tonne in official open outcry activity. It earlier touched $1,914, the strongest since March 4.

Zinc prices fluctuated wildly and Shanghai Futures Exchange (ShFE) spreads ballooned after Li said a planned cut in value-added tax (VAT) on China's manufacturing sector, which includes non-ferrous metals, would take effect from April 1. Some speculators on the ShFE had previously bet that the planned cut in VAT would be implemented on May 1, increasing the backwardation on metals, including copper and aluminium.

The backwardation between the March and April ShFE copper contracts spiked to over 1,000 yuan a tonne, the highest since May 2014, after Li's comments. The spread between April and May, previously in a steep backwardation, immediately flipped into a deep contango.

LME zinc spiked 2 per cent to $2,882 a tonne, the highest since July 2, immediately after Li's comments, before profit-taking saw the metal used to galvanise steel drop 1.2 percent to trade at $2,792.50 a tonne in official rings.

It is still on course for a 3 per cent gain this week, which would be its best week in six, as investors worry about tight stocks.

The premium for cash zinc over the three-month LME contract stood at $55 a tonne at Thursday's close, the highest since early January.

Copper inventories have surged 67 per cent over the past two days, weighing on the price. LME copper, untraded in rings, was bid down 0.1 per cent at $6,400 a tonne.

Nickel was bid 0.5 per cent firmer at $12,945 a tonne, lead was bid down 1.9 per cent at $2,074 and tin traded up 0.1 per cent to $21,200.