"China's economy and demand is slowing, the dollar isn't helping and Chinese authorities are intent on making sure the market understands what they want"
Prices have rocketed 25% this year as commodities and equities markets surged and investors anticipate that a crackdown on polluting smelters in China will constrain supply.
Adding impetus was China saying it would "indefinitely" suspend all activity under a China-Australia Strategic Economic Dialogue, deepening a crisis in relations.
Benchmark aluminium on the London Metal Exchange was up 1% at $2,387 a tonne at 1121 GMT. Prices of the metal used widely in the transport, construction and packaging industries earlier touched $2,389, a gain of more than 20% since January.
Electricity, much of it from coal in China, can account for 30%-40% of aluminium smelting costs.
Benchmark aluminium on the London Metal Exchange (LME) was up 1% at $2,315 a tonne.
Aluminium, which is used in transport, packaging and construction, earlier touched its highest since June 2018 at $2,323.50 to stand more than 15% up from the start of this year.