President Bush yesterday set a goal to curb growth in US carbon emissions over the next twenty years, but earned further condemnation from environmentalists for failing to provide sufficient details on how this target would be attained.

In a heavily trailed speech, Bush set a goal of 2025 for slowing carbon emissions growth in the US to zero, arguing for declining emissions after that. However, the targets were predicated on other countries matching that commitment, he said.

He outlined a plan for aggregating incentives for different energy types, including nuclear power, into a single programme, which would then weight incentives according to their emissions.

Bush emphasised his support for a voluntary incentive-based scheme rather than regulatory measures. He also took a thinly veiled swipe at the proposed Lieberman-Warner Act, which aims to tackle climate change through binding emission targets and comprehensive cap-and-trade systems, warning Congress against over-regulating industry.

"Bad legislation would impose tremendous costs on our economy and on American families without accomplishing the important climate change goals we share," he said. "The wrong way is to raise taxes, duplicate mandates, or demand sudden and drastic emissions cuts that have no chance of being realised and every chance of hurting our economy."

Last October, the Climate Security Act 2007 was introduced by Senators Joe Lieberman and John Warner, demanding a freeze on emissions growth by 2012 and a 62 per cent reduction by 2050.

Greenpeace US executive director John Passacant argued that other regions have already exceeded the goals Bush stated yesterday. "Stopping growth in US emissions by 2025 is completely inconsistent with what scientists say is necessary to stop catastrophic global warming," he said. "In fact, Europe has agreed to reduce its emissions 20 per cent and pledged to cut 30 per cent by 2020 if the US makes a comparable commitment. The time has come to look beyond President Bush and towards the next occupant of the White House for leadership and vision on global warming."

Bush will likely take the broad plan to a G8 meeting in July, where leaders will discuss a framework for curbing carbon emissions following Kyoto's expiration in 2012.