For months, investors have been looking to base metals exchange traded funds (ETFs) as a sign of where the global economy is heading. But renewed concerns about demand from China could have the funds sitting idle for the time being.

Yesterday, most metals finished lower after China made more moves to curb lending and rein in growth. Several large banks in the country were singled out and required to raise their reserve ratios, reports Nick Godt for MarketWatch.

Copper was especially feeling the pressure and futures declined nearly 2% in trading today. Copper could be hit hard if tightening in China translates into reduced demand for the metal. The dollar also strengthened yesterday, further tamping down demand, reports Allen Sykora for The Wall Street Journal. [Opportunities in other metals?]

Metals like copper, silver and aluminum have benefited in recent years from the huge increase in demand, particularly from China. As the global economic recovery deepens and emerging nations industrialize, many believe that demand for these metals should continue in the long run. [A deeper look at copper and its near future.]

Among the believers is the International Monetary Fund (IMF), which said today that it expects commodity prices to continue to rise amid recovery. In the short-term, though, base metals may be taking their cues from the dollar, economic numbers and the overall risk appetite in the markets, reports Commodity Online.