"The subsidies we want to prohibit maintain inefficient production capacity in industries ranging from steel to semiconductors," US Trade Representative (USTR) Susan Schwab said in a statement.

"Stronger rules for these types of subsidies would address significant trade-distorting practices of many of our trading partners that often lead to unfair trade," she said.

The US proposal would prohibit five types of subsidies if they are "specific," that is only given to a particular company or industry, and benefit a product that is exported or competes with imports, the trade office said.

The proposed practices to be prohibited are coverage of operating losses; forgiveness of government-held debt; lending to "uncredit-worthy" companies; equity investments in "unequity-worthy" companies; and other financing, such as "royalty-based" financing that is not commercially available.

The proposed new subsidy rules were not intended to apply to the agriculture sector, the trade office said.

The proposal also seeks additional WTO transparency procedures applicable to state-owned companies and government subsidies to such companies.

The USTR said it had submitted the proposal Monday to the WTO rules negotiating group for the Doha Round negotiations, which were suspended in July 2006 for lack of progress but unofficially resumed in January.

The US proposal comes ahead of key talks this month in Germany between the four major WTO powers -- US, the European Union, Brazil and India -- in a bid to energize the Doha Round.

The meeting of the so-called "G4" group will take place in Potsdam, outside Berlin, but the precise date has yet to be fixed, according to diplomats.