RAN pointed a finger at the institutions last Monday outside a meeting of the Carbon Disclosure Project, which monitors corporate disclosure related to climate change.

Brianna Cayo Cotter, a spokeswoman for RAN, said the group had been talking about the issue with big US financial institutions for several months.

She said the San Francisco-based environmental group will name the targeted banks when it launches its campaign against coal financing next Tuesday.

Financial giants are coming under increasing fire from environmental groups and investors who complain they still fund power plants and other polluting projects, despite adopting the Earth-friendly Equator Principles with much fanfare in 2003.

"People across the country are waking up to the threats posed by coal -- the world's dirtiest, most carbon-intensive and most heavily used energy source -- and demanding that it be replaced by energy efficiency and clean, renewable energy sources like solar and wind," RAN said in a statement.

It said it was fighting to stop an estimated 150 proposed coal-fired power plants currently in development across the United States.

"Coal power is the leading source of greenhouse gas emissions in the United States and a top contributor to air pollution, asthma and ecological destruction," RAN said. "Coal extraction through mountaintop removal and strip mining is devastating communities and ecosystems in Appalachia and the Southwest."

The group said it will reveal Tuesday "which banks are most responsible for underwriting the worst coal companies and what the banks can expect from a public campaign to stop their investments in coal development."

There is an estimated 200-years worth of coal reserves in the United States. It generates about 50 percent of the country's electricity and is expected to play a greater role as power demand increases and the country moves to wean itself more of foreign oil.

Coal companies are actively working to develop cleaner fuel that will burn more efficiently with lower carbon emissions. They are also working on new technologies such as coal-to- liquids, which could produce liquid fuel for aircraft.

Citigroup is directing US$50 billion over 10 years to address global climate change and has invested in Sindicatum Carbon Capital, which develops projects that cut greenhouse gases. Bank of America has pledged to invest US$20 billion over 10 years in green business.