By Bob Howard
BBC Radio 4's Money Box
The rising price of copper has prompted the US government to consider making coins with cheaper metals.
Dealers shout out prices at the London Metal Exchange
The price of copper has risen to just under $8,000 a tonne, driven by demand from countries like China and India.
The US Mint says it is now costing as much as 1.7 cents to produce a "penny" (1 cent) and 10 cents to produce a "nickel" (5 cents).
Reducing the amount of metal used making these coins could save the US government around $100 million a year.
If this was extended to higher denomination coins, the savings are estimated at $400 million.
At the moment, only the US Congress has the power to change the metal composition of US coins.
The proposal by members of the US Senate and House of Representatives would give these powers to the US Treasury.
Greg Hernandez, Deputy Director of Public Affairs for the US Mint says change is on the cards:
"If the world demand continues to be high for copper, nickel and zinc, then if this legislation is approved, the metal content for the penny and the nickel will be quite different from what it is today."
In April, the US government finally passed a law to make it illegal to melt down US coins, or export them in any quantity abroad.
Any wide-spread withdrawal of pennies and nickels could cause coin shortages
Greg Hernandez, Deputy Director of Public Affairs for the US Mint
Anyone doing so now faces a fine of up to $10 000, in conjunction with five years in prison.
Greg Hernandez says action was taken after the US Mint started receiving enquiries from the public as to whether it was illegal to melt down US coins.
"It was to safeguard against a potential shortage of these coins in circulation, because any wide-spread withdrawal of pennies and nickels could cause coin shortages, and that would be extremely costly to replenish, given the prevailing metal prices and production costs"
In India, the government has had to take action after rupee coins were illegally melted down in order to make razor blades.
The Australian Royal Mint has warned its citizens it is illegal to melt down Australian dollars.
The British Royal Mint changed the composition of its one and two pence coins in 1992 from bronze (97% copper) to copper-coated steel.
It has confirmed that the value of the copper in pre-1992 one penny and two penny coins is now greater than the face value.
Royal Mint figures suggest there could be more than eight billion pre-1992 one and two pence coins still in circulation.
However, anyone trying to melt them down could face a fine or two years in prison.
BBC Radio 4's Money Box was broadcast on Saturday, 27 October 2007 at 1204 BST.