Canada's prime minister is reversing his position and will attend a United Nations climate change conference in Copenhagen next month, Stephen Harper's spokesman said Thursday.

Dimitri Soudas announced Harper decided to attend one day after U.S. President Barack Obama and Chinese Premier Wen Jiabao announced their attendance at the U.N. talks. Soudas said Harper's decision was based on the fact that now "a critical mass of world leaders will be attending."

Soudas did not indicate on what day or days Harper would be there.

Harper's participation at the conference is a change of course for Canada's Conservative government, which has consistently downplayed expectations for the conference, where it was hoped the global community would agree on a successor treaty to the Kyoto Protocol.

Only a week ago at an Asia-Pacific Economic Cooperation summit in Singapore, Harper told reporters that the assembled leaders shared "a pretty strong consensus . . . that the countries of the world remain a long way from a binding, legal treaty on climate change."

But with U.N. Secretary-General Ban Ki-moon and Danish Prime Minister Lars Lokke Rasmussen both attending a Commonwealth summit this weekend to push the climate issue, Harper may have felt pressure to participate in a global strategy to curb global warming.

The Conservative leader pulled Canada out of the Kyoto Protocol, a 1997 accord to fight global warming by reducing greenhouse gas pollution, after he was elected in 2006. Since then Canada has come under strong criticism internationally for reneging on the treaty and for refusing to sign on to a new deal limiting greenhouse gases unless developing nations are included.

Harper has called on Obama to agree to a new North American climate change pact, saying it's difficult for one country in a shared economic space to set policies independent of its neighbor, but no formal agreement has been put in place.

The United States agreed to emission reductions in the Kyoto pact but never implemented them because of strong political opposition at home. The U.S. never ratified the Kyoto agreement.

Under the original Kyoto accord, signed by the previous Liberal government, Canada committed to cutting emissions by 6 percent from 1990 levels by 2012. Output of greenhouse gases is now around 35 percent higher than 1990 levels.

The Conservative government says it plans to cut greenhouse gases by 20 percent by 2020 from 2006 levels, which are actually slightly tougher than Obama's vow to reduce emissions by roughly 17 percent below 2005 levels by 2020.