Russian President Vladimir Putin has dashed hopes that he would set a date this week for Russian ratification of the Kyoto protocol to curb global warming. Opening a major international conference on climate change in Moscow, Mr. Putin said Russia needs more time to consider the issue.

President Putin said his government must consider the social and economic consequences of signing the Kyoto protocol, which aims to reduce emissions of various gases believed to cause global warming. He says his government's decision will be based on Russia's interests.

President Putin also urged that the interests of other nations be taken into account when addressing issues of global climate change.

Mr. Putin said any efforts to resolve the problem of so-called greenhouse gases believed linked to global climate change must not cause more problems, particularly for developing nations.

He said Russia had already helped relieve the problem of global warming by reducing its atmospheric emissions by more than 30 percent since 1990.

In a written message sent to conference participants, U.N. Secretary General Kofi Annan said he looked forward to Russia's ratification of the Kyoto protocol. "I join peoples throughout the world in eagerly awaiting ratification by the Russian Federation, which will bring the protocol into force and further galvanize global action," he said.

The 1997 Kyoto pact must be ratified by at least 55 countries accounting for 55 percent of global emissions. With the United States withdrawing from the pact last year, Russia's ratification is considered essential to reaching the minimum.

Russian officials have recently made it clear they hope to derive economic benefits from ratifying the pact.

In statements released on the eve of the conference, environmentalists criticized Russia for failing to set a date for ratification. The group Greenpeace said Russia has had more than three years to analyze how the Kyoto treaty could be implemented and that by stalling now Russia is threatening to derail the entire process.

The World Wide Fund for Nature (WWF) took a stronger tone. Its statement said President Putin has to decide if he wants his nation to be known as a "climate killer."

More than 100 nations have signed the Kyoto protocol to reduce emissions of gases like carbon dioxide, which has been blamed for higher global temperatures, as well as for causing heat waves, floods, and droughts.