(Bloomberg) -- Copper held this week’s gains in London, with investors weighing the impact of the US-China trade war. Chinese markets reopened following the Lunar New Year break.

Beijing imposed retaliatory tariffs on a range of US products on Tuesday and announced an investigation into Google, moments after US President Donald Trump imposed a 10% levy on Chinese imports. China put export controls on several niche metals — most notably tungsten — in a further show of its dominance in critical minerals.

Base metals have endured a bumpy start to the year, buffeted by trade-war fears, as well as concerns about tepid demand in China, the top consumer. While a prolonged trade war could damp economic growth in Asia’s largest economy, there’s also speculation that Beijing will step up stimulus efforts, which may be positive for metals consumption.

It will take a while for Chinese demand to recover after the holidays, Shanghai Metals Market said in a note. And there are concerns around global trade frictions and economic growth, it said.

Copper was up 0.3% at $9,178 a ton on the London Metal Exchange as of 9:01 a.m. local time after gaining for two days. Aluminum fell 0.8% while tin climbed 1%.

On Chinese markets, zinc led declines, falling by 1.7% to the lowest since September in the first session since Jan. 27. Copper dropped 0.3% in Shanghai and aluminum was steady.

Copper is the only metal where there is a significant trade between China and the US. Around 40% of American copper scrap exports and 16% of concentrate shipments go to China, Macquarie analysts led by Marcus Garvey said in a note.