Nine northeastern US states, including New York and New Jersey, are reviewing a preliminary proposal that would force power plants to cut greenhouse gas emissions by 10 per cent by 2020, according to officials familiar with the proposal.

If agreed, the proposal could represent a bold attempt by a group of states to set their own greenhouse gas reduction targets, in the absence of a wider federal plan. The Bush administration has said it supports clean energy technologies, but not regulatory limits that would enforce a reduction in the pollutants that contribute to global warming.