Moscow ? In what would be a mortal blow to the accord aimed at halting global warming, a top Kremlin official said Tuesday that Russia would not ratify the Kyoto Protocol limiting greenhouse gas emissions because it would hurt the country’s economy.

The United States rejected the accord for the same reason. Without Moscow, the protocol cannot come into effect even if approved by every other nation because only Russia’s industrial emissions are large enough to tip the balance.

The pollution cuts required by the treaty would slow the economic growth that President Vladimir Putin has made a major priority, said top adviser Andrei Illarionov.

“In its current form, the Kyoto Protocol places significant limitations on the economic growth of Russia,” Illarionov told reporters in the Kremlin on the sidelines of Putin’s meeting with European business leaders. “Of course, in its current form this protocol can’t be ratified.”

Earlier this fall, Putin cast deep doubts on Moscow’s willingness to ratify the protocol, but he had not ruled it out entirely.

A Russian Economics Ministry spokesman, Konstantin Bogdanov, told Dow Jones News Wires on Tuesday he was unaware of any change in Russia’s official position, which has been that it is still considering the protocol.

However, Illarionov said it would be unfair for Russia to curb emissions and stymie its own growth while the United States and other nations, which account for the bulk of global emissions, refuse to join the pact.

Putin laid out Russia’s objections in what Illarionov called a “very energetic” discussion with the European industrial leaders.

The Kyoto Protocol, signed by many of the world’s nations at a conference in Japan in 1997, sets targets for countries to reduce emissions of carbon dioxide and other greenhouse gases, which are seen as a key factor behind global warming.

To take effect, the pact requires ratification by a minimum of 55 countries, which must include the industrialized nations that accounted for at least 55 percent of that group’s carbon dioxide emissions in 1990.

So far, industrialized nations that have signed on account for 44.2 percent of the 1990 emissions. Russia accounts for 17.4 percent, so its ratification would push the group over the top.

Putin has called for the doubling of Russia’s gross domestic product by 2010 — a goal officials fear might conflict with the Kyoto Protocol, which would require the Kremlin to overhaul Russian industries to cut emissions.

Russia’s emissions have fallen by 32 percent since 1990 amid the post-Soviet industrial meltdown, but they have slowly started to rise with the economic revival of the past five years.