Government data showed fewer-than-expected unemployment applications being filed last week, the lowest in 15 years.
Policymakers tend to have more room to manoeuvre in an expanding economy, which tarnishes the precious metal's appeal as it generally only offers returns through price gains.
Signs that copper supplies are tightening and speculation that China's economy is rebounding have analysts saying the metal has entered a bull market.
Factors such as a tight market at the refined level, a lack of concentrates, labour disruptions risking global output have contributed to this view.
SNL Metals and Mining metals consultant Paul Dewison said that the metal "seems to be blessed" and expects "a little over" 200,000 tonnes being added by the State Reserves Bureau (SRB) in 2015.
So far copper has averaged $US5,889.32 ($A7,457.97) and settled at $US6300 ($A7,979.45) on Wednesday.