London Metal Exchange metals closed mostly lower as the ongoing partial government shutdown in the US fueled mounting concerns that the suspension of federal activity may have an impact on economic growth and demand for materials.
A stronger US dollar also dented the appeal of the dollar-denominated base metals to buyers holding other currencies, as market participants digested the news that Janet Yellen will be nominated to lead the Federal Reserve and looked toward minutes from the US central bank's September meeting.
At the close of open-outcry trading in the LME ring, copper was down 1.9 per cent at $US7,099 a metric ton.
Aluminum fell 0.4 per cent to $US1,857.50 a ton.
"The dollar's recovery overnight has seen the base metals complex under pressure," said RBC Capital Markets in a note.
US political leaders have made little progress toward resolving the budget impasse in Washington, also pressuring the risk-related industrial metals lower.
A protracted government shutdown could hit copper demand, as the temporary pay pauses to some federal workers and a loss of funding for government programs could limit economic activity in the world's second largest copper consumer.
Additionally, some investors are worried that the deadlock over the budget issue suggests the chances are slim of politicians reaching an agreement to lift the US borrowing limit before the October 17 deadline.
Recent downgrades to global economic growth expectations were also weighing upon base metals and on hopes for better demand.
Trading volumes remained somewhat thinned with market participants in London for the London Metal Exchange's annual industry gathering.