"The first phase of the protocol ends in 2012, after that it is unthinkable to go ahead without the United States, China and India," Matteoli told reporters at Kyoto-related talks in Buenos Aires in quotes confirmed by his ministry on Wednesday.

"Seeing as these countries do not wish to talk about binding agreements, we must proceed with voluntary accords, bilateral pacts and commercial partnerships."

The United States, which emits a quarter of the world's and one third of the developing world's greenhouse gas, pulled out of the pact in 2001 saying it would harm the economy and was unfair as it did not set targets for developing countries.

But the EU ploughed ahead and secured the backing of other big emitters Japan and, just last month, Russia.

Under the pact, developed countries must reduce their emissions by an average of 5.2 percent of 1990 levels by the period 2008-12, a commitment which the ministry said Italy intended to honour.

Signatories are expected to sign up for bigger cuts in a second period after 2012 in a rolling process aimed at bringing emissions down to levels that will not affect the climate, considered to be at least a 60 percent global cut.

Kyoto decrees that signatories must start discussing their post-2012 commitments by next year at the latest. The pact's backers have always assumed this would mean more, bigger emissions cuts, something Italy has now put in doubt.

CALL TO RESIGN

Italy's EU partners played down the idea that the minister's comments signalled a change in policy.

"What the Italian minister said is quite right. We have to involve the fast-growing developing countries and the United States in the after-2012 regime," said Dutch Environment Minister Pieter van Geel, who is heading the EU delegation in Buenos Aires.

He did not say whether the EU no longer sought binding emissions reduction commitments after 2012. EU leaders are due to discuss post-2012 climate strategy at a summit in March.

Italian environmentalists accused the government of Prime Minister Silvio Berlusconi of abandoning Kyoto and cosying up to President George W. Bush, who he met in Washington later on Wednesday.

The head of Italy's green party called for Matteoli's resignation. "Never in recent years has Italy embraced in such a servile way the most anti-environmental positions of the Bush administration," Alfonso Pecoraro Scanio said.

Bush's other main European ally, British Prime Minister Tony Blair, who becomes leader of the group of eight nations in January, plans to put climate change on top of the agenda and work to bring the United States back into the global effort.