Germany and other European countries have been calling on the US to adopt firm targets for cutting carbon dioxide emissions.
Merkel has proposed a commitment to cutting global greenhouse gas emissions to 50 per cent below 1990 levels by 2050 and limiting the worldwide temperature rise this century to two degrees Celsius.
Washington has strongly objected to the draft declaration.
"The way to meet this challenge of energy and global climate change is through technology and the United States is in the lead," Bush said.
The US plan would see countries set "mid-term national targets and programmes" depending on "their own mix of energy sources and future energy needs".
The strategy was met with scepticism by environmental groups.
"This is a transparent effort to divert attention from the president's refusal to accept any emissions reductions proposals at next week's G8 summit," Philip Clapp, president of the US-based National Environmental Trust, said.
"After sitting out talks on global warming for years, the Bush administration doesn't have very much credibility with other governments on the issue."
The US is the world's largest producer of greenhouse gases and has refused to ratify the Kyoto Protocol, which requires signatories to make targeted cuts in emissions.
Charlie Kronick, climate change expert a Greenpeace, said: "The only way you can get a grip on carbon emissions is to cap and trade them globally.
Bush has rejected that, so there are fundamental contradictions in these declarations."
"This is utterly nonsensical. There is a con at the heart of the way that the US is approaching this. Unless they are willing to participate in the global efforts to reduce carbon emissions, the rest of the world is going to have to go on and make a framework which the US can join later."
Series of meetings
Bush plans to hold a series of meetings on ways to limit global emissions by a set amount by about 2050.
About 15 countries would be invited, including two nations that like the US are major polluters, China and India.
Those two developing nations are exempt from the mandatory targets and Washington has cited this as a reason for not submitting the protocol for ratification by the US senate.
UN negotiations on a new protocol on climate change to replace Kyoto will begin in earnest at a conference in Bali in December.