Sweden's prime minister, Fredrik Reinfeldt, called on Monday for more pressure on the United States, China and India to commit to action to tackle global warming.

Reinfeldt, opening a week-long conference on water in Stockholm, said the European Union was a key part of the process to address environmental challenges and reduce so-called greenhouse gasses.

But he added, "The European Union is not enough to make change. We need to make the United States, China, India and other countries to commit themselves to actions."

Reinfeldt said climate negotiations will be at a decisive stage in 2009.

"With this said, I'm optimistic about the years ahead of us. Today we see the awareness of global warming," he said.

"What becomes apparent is that climate change hits us first through water. We know that the changes will happen," the prime minister said.

Reinfeldt cited statistics showing more than one billion people already lacked access to safe drinking water and more than 2.4 billion lacked access to basic sanitation. But he said progress was being made.

Between 1990 and 2002, he said, the share of the world's population with safe drinking water had risen to 79 percent from 71 percent.

Anders Berntell, executive director of the Stockholm International Water Institute, told the conference that improvements were not coming fast enough.

"At the current rate, the target of halving the proportion of people without basic sanitation by 2016 will be missed by 600 million people, with the net result that at least two billion people will still be without adequate sanitation."