By Gerard Wynn

LONDON (Reuters) - U.S. banks, industry and decision makers are holding open talks about the shape of future climate regulations in the United States, likely to have far-reaching impact on the economy, bankers say.

The main idea of any climate change regime is to put a price on carbon emissions, for example with a carbon tax, or subsidize alternative, low carbon-emitting energy technologies like solar power, or both.

The European Union leads the world in national policies to curb greenhouse gas emissions with its emissions trading scheme, but the United States is expected to table its only federal policies under a new U.S. administration to succeed President George W. Bush from 2009.

Bankers are getting excited about a U.S. carbon market which would impact the profitability of energy-intensive companies and potentially swell the revenues of banks' trading floors.

"That's why banks are investing (in carbon markets)," said Bruce Tozer, global head of environmental markets at JP Morgan.

"This could be completely ubiquitous in banking...in pension fund valuations, M&A," he said on the sidelines of a clean energy conference in London, organized by research group New Energy Finance.

A carbon market works by setting an overall cap on emissions of planet-warming greenhouse gases but allowing companies to trade emissions permits among themselves.

The U.S. Congress is considering several bills that aim to launch a similar, federal U.S. cap-and-trade market to the European scheme, that would reward industries for cutting emissions.