SHANGHAI: Shanghai copper registered a second consecutive month of gains on Monday as prices firmed on a potential supply threat in Chile and massive US infrastructure spending plans.

Copper is often considered a bellwether of the global economy because of its wide usage across different sectors.

The most-traded July copper contract on the Shanghai Futures Exchange closed 0.9% up at 73,950 yuan ($11,617.68) a tonne for a 2.1% monthly gain.

A strike by a union of remote operations workers at BHP's Escondida and Spence copper mines in Chile entered its second day on Friday, with the company using replacement workers to ensure continued production.

The White House, meanwhile, has proposed a $6 trillion budget plan to ramp up spending in several sectors including infrastructure.

"Copper received a boost after the Biden administration proposed an infrastructure-fuelled surge in government spending. Prices are also being supported by rising supply side issues," ANZ analysts said in a note.

ShFE nickel advanced 1.7% to 132,890 yuan a tonne, tin climbed 1.8% to 209,000 yuan, aluminium rose 0.5% to 18,825 yuan and lead firmed by 0.7% to 15,625 yuan.

Trading was muted, however, with the London Metal Exchange (LME) closed for a public holiday.

Democratic Republic of Congo has authorised exports of copper and cobalt concentrate for mining companies that hold waivers, customs documents showed, after the country appeared to issue a blanket ban on them.

Bottlenecks at LME-registered warehouses in Malaysia owned by metals storage firm ISTIM UK are adding to difficulties facing aluminium consumers in the United States and Europe in securing supplies.