"We think that United States of America make a big mistake not signing the Kyoto protocol," said Francesco Ferrante of Italy's Environment League.

Standing outside the United States Embassy in Rome, a group of environmentalists waving flags voiced their disagreement with Washington for its failure to ratify the Kyoto protocol on reducing greenhouse gas emissions.

The treaty, which was signed in the ancient Japanese capital in 1997, takes effect Wednesday.

Mr. Ferrante said greenhouse gases are causing climate changes and the United States is one of the world's greatest polluters.

"The fact that there is no engagement in the United States to reduce these gases is a very bad thing for all the planet," he said.

Mr. Ferrante added that signing the Kyoto protocol goes in the right direction to slow down global warming.

The president of the Environment League, Roberto Della Seta, said Wednesday would be a historic date for the planet. Each government, he said, will have to show it believes in the commitment it has undertaken to radically reverse its energy policies.

The United States, like Australia, has not signed the treaty claiming that the burden to their economies caused by Kyoto would be too great. The Bush administration prefers setting voluntary emission limits for U.S. companies and more research on new energy technologies. The administration also thinks rapidly industrializing countries, such as China and India, should meet the same emissions standards as developed nations.

A total of 141 countries have ratified the treaty, which demands a 5.2 percent cut in greenhouse gas emissions from the industrialized world as a whole, by 2012. Each country has been given its own individual targets according to its pollution levels.