Tony Blair says he hopes to bring US President George Bush back into talks about ways of fighting global warming as the Kyoto Protocol comes into force.
Mr Blair says action is needed now to avert a catastrophe
Some 141 countries - who account for about 55% of greenhouse gas emissions - have ratified the treaty, which pledges to cut these emissions by 5.2% by 2012.
Mr Blair said global warming could be "a catastrophe" if not addressed now.
The Lib Dems want Labour and the Tories to make an environmental commitment. The Greens condemn the US over Kyoto.
He spoke as the Kyoto Protocol, which aims to slow global warming, came into force 90 days after Russia's crucial decision to ratify it in November 2004.
The US and Australia have abstained for economic reasons, and developing countries such as China and India are outside its framework.
Mr Blair said the problem of global warming could become "a catastrophe" for some parts of the world if it was not addressed now.
He said the "only solution" was to bring the Americans back into talks and make sure China and India, which have populations of over one billion each, get on side.
"If the science is right, then not immediately, but growing over a period of time - certainly over 30-40 years, well within the life-time of my kids, this is going to be a major, major issue," he told Five's The Wright Stuff show.
"It's going to cause difficulty, if not catastrophe, for parts of the world and will also affect our own.
"The only solution, I'm afraid, is we have got to pull the Americans back into dialogue."
Mr Blair said investment in science and technology was necessary if people were going to carry on consuming and see living standards grow without damaging the environment.
"If we don't do it now, as the wealthy countries, how are we going to be able to say to China and India when they will be the big economic players in 30-40 years time, you have got to consume less because of what we've done in the past?
"What I'm trying to do, later this year, is make sure we pull America back into a dialogue and put China and India alongside that."
The Kyoto Protocol, which became a legally binding treaty at midnight New York time (0500 GMT) on 16 February, demands a 5.2% cut in greenhouse gas emissions from the industrialised world as a whole, by 2012.
Each country has been set its own individual targets according to its pollution levels.
The UK has beaten its 12.5% target to reduce emissions, but is not on track to reach its ambition to reduce these by 20% in 2010.
Environment Secretary Margaret Beckett described the agreement as "a very small first step" towards slowing global warming.
She said she doubted whether in the short term Britain would look to returning to a greater use of nuclear power despite it being a carbon free technology.
"I don't, however, rule out the fact that there may come a day when that is so. I don't expect it to be in the near future," she told BBC Radio 4's Today programme.
Meanwhile, Liberal Democrat leader Charles Kennedy has challenged Mr Blair and Michael Howard to make a commitment to the environment.
He urged both leaders to sign a statement of intent, arguing that the UK should commit to meeting its Kyoto targets of reducing emissions by 20% by 2010 and by at last 60% by 2050.
But Green MEP Caroline Lucas said the international community should find ways of "holding the US accountable for the damage its isolationist policies are inflicting on the rest of the world".