By Richard Black
BBC environment correspondent
The European Union says it will push for legally binding global restrictions on greenhouse gas emissions.
The EU plans to pursue legally binding restrictions
A spokeswoman's comments came after the announcement of a voluntary pact, based on new technology, between the US and five Asia-Pacific states.
She also told BBC News that the new pact was unlikely to bring a significant reduction in emissions.
The EU's intention to pursue further legally binding reductions could lead to political disputes later this year.
The new pact will allow signed-up countries - currently the United States, Australia, China, India, South Korea and Japan - to set goals for reducing greenhouse gas emissions individually, with no enforcement mechanism.
The core approach is to develop clean technologies, such as low-emission coal-fired power stations, which can be used in developing countries as their energy needs increase.
The signatories argue it complements, rather than weakens, the 1997 Kyoto agreement, which imposes targets on industrialised countries to cut their emissions.
Speaking at the announcement, which came during the Regional Forum of the Association of South-East Asian Nations (Asean) in Laos, US Deputy Secretary of State, Robert Zoellick, said the six nations "view this as a complement, not an alternative" to Kyoto.
Both the US and Australia have refused to ratify Kyoto, which came into effect earlier this year - partly, they say, because big developing countries like India and China escape emissions limits.
Australian Foreign Minister Alexander Downer told BBC News: "Our view is you really need to focus on technological change to solve the climate change problem... and you do have to involve the major developing countries, which are very substantial emitters."
A Chinese spokesman called the pact a "win-win solution" for developing countries.
But environmental groups argue that the new agreement undermines the Kyoto Protocol, and will make the process of agreeing a successor treaty more difficult. The Geneva-based Worldwide Fund for Nature (WWF) said: "A deal on climate change that doesn't limit pollution is the same as a peace plan that allows guns to be fired."
The European Commission's environment spokeswoman Barbara Helferrich told the BBC News website that Europe remained committed to further legally binding reductions in emissions.
"We welcome any initiative that can combat climate change, but this has to be seen in a global context," she said.
"If it is simply technology and clean coal, it is no substitute for agreements like the Kyoto Protocol and we do not expect it to have a real impact on climate change.
"There will have to be binding global agreements, but on what scale and what basis is yet to be decided."
The designated forum for making those decisions is the next round of United Nations climate negotiations, which opens in Montreal in November - shortly after the Asia-Pacific grouping holds its first meeting in Adelaide.
There is concern in environmental circles that the United States and Australia will present the new pact as evidence that a "son-of-Kyoto"-style treaty is not needed.
Europe, which for many years has been the leading pro-Kyoto force, is unlikely to agree.