As the Kyoto agreement on global warming comes into effect, Tony Blair has said he is determined to pull the United States "back into dialogue" over the need to tackle climate change.

The prime minister reaffirmed his commitment to making the issue a key priority for Britain's presidency of the G8 group of industrialised nations.

In an interview on Channel Five's The Wright Stuff, Blair said: "I think the science is very clear. Certainly in 30, 40 years - well within the lifetime of my kids - this is going to be a major, major issue.

"It is going to cause difficulty, if not catastrophe."

The Kyoto protocol, which has taken seven years to come into force, requires dozens of industrial nations to reduce emissions of greenhouse gases believed linked to climate change.

China, India and the US - the world's biggest emitter of carbon dioxide - are among the countries which so far remain outside the treaty.

Blair said: "What I am trying to do later this year is to make sure we pull America back into a dialogue and put China and India alongside that and if we manage that I think we will get back on the right track."

Economic growth

The prime minister sought to reassure the US that reducing greenhouse gas emissions did not mean cuts to living standards and economic growth.

"If we made the investment in the science and technology now we could probably find that we could carry on consuming, seeing our living standards grow without doing real damage to the environment," he said.

"If we don't do it now, how are we going to be able to tell China and India - who will be the big economic players in 30, 40 years' time - to consume less because of what we have done in the past?"

A first step

Environment secretary Margaret Beckett has maintained that the Kyoto protocol is an important first step in cutting greenhouse gas emissions - despite the US's non-compliance.

Speaking on BBC Breakfast, she said: "The Kyoto protocol is worth a great deal, not least because it is the first real sign of an international and legally binding agreement among many of the world's most developed countries to actually start to take action to cut greenhouse gas emissions."

"To realise the real significance we just have to imagine what it would be like if the Kyoto Protocol had not come into force.

"People would be saying: ‘What can we do?’ We would have to start all over again."

"It is perfectly true that the Kyoto Protocol is a very small first step. I think anybody involved in negotiating that step knows just how difficult it has been but that first step is crucial."

A win-win scenario

Shadow environment secretary Tim Yeo said the Kyoto deal had "serious flaws" - most notably the absence of the US - but hailed it as an important step in tackling climate change.

Talking to the BBC Radio 4 Today programme, Yeo said: "The longer we delay responding to the problem the more expensive the response will have to be.

"The trick now is to encourage the faster introduction of new technology - things like greener cars; to use those which are essentially commercial opportunities as a big part of our solution to the problem of climate change.

"If we do that, I think we can achieve the win-win scenario of continued economic growth, which is crucial for the developing countries, while at the same time not damaging the planet.

"But in doing all that we have to be careful not to overburden individual countries unfairly."

Cross-party consensus

Liberal Democrat leader Charles Kennedy challenged the leaders of the other major parties to sign up to even tougher climate change targets.

In a letter to Tony Blair and Michael Howard, Kennedy urged them to go further than the Kyoto environmental pact.

The Liberal Democrats say the UK should commit to meeting its Kyoto targets ahead of the deadline and pledge that Britain will reduce carbon dioxide emissions by 20 per cent by 2010 and by at least 60 per cent by 2050.

In his letter Mr Kennedy said: "With the Kyoto agreement coming into force, this is an important and historic moment in the fight against climate change.

"The Kyoto treaty is only the start of the process. If we are to tackle climate change, then concerted and consistent action on the international stage - and at home - will be required for decades to come.

"In this country we are lucky that there is no disagreement between the political parties that climate change represents a grave threat to the planet and must be addressed."

He added: "There is a great deal of cross-party consensus on how to take forward the green agenda."

"It is my firm belief that Britain is most likely to succeed abroad when our international policy is the product of a strong national consensus at home, when our national political debate is mature and self-confident," he said.

"This is an issue which transcends elections and party colours and in the light of the seriousness of the threat we face, the three parties should come together to agree a common platform."