Washington  - The United States will push for more restrictions on tourism to the North and South Poles to protect the regions' natural environment and avoid the worst effects of global warming, US Secretary of State Hillary Rodham Clinton said Monday.

Opening a nearly two-week summit bringing together the two diplomatic bodies that govern the Arctic and Antarctic, Clinton warned that protecting the region was crucial to stabilizing the global climate.

"The changes under way in the Arctic will have long-term impacts on our economic future, our energy future and indeed again the future of our planet, so it is crucial that we work together," Clinton said at an opening ceremony at the State Department in Washington.

The gathering, which brings together scientists and government officials from 47 countries, marks the first US-hosted summit on the environment since President Barack Obama took office in January, and comes as world governments are hoping to reach a new deal by December to curb the pollutants that cause global warming.

This week's summit, which moves to Baltimore, Maryland, after Monday's opening ceremony, will review the latest science, the impact of tourism and protecting the environment and species in the polar region.

"Strengthening environmental regulation is especially important as tourism to Antarctica increases," Clinton said, proposing limits on larger ships and increasing safety and environmental regulations.

Scientists have warned that global warming is already having a significant impact on the world's polar regions. Melting Arctic ice could cause a dangerous rise in global sea levels, flooding some coastlines and accelerating the impact of climate change around the world.

A study by US space agency NASA released on the sidelines of the polar summit found that Arctic ice was melting, and thinning, at a faster rate than expected. About 70 per cent of the Arctic's sea ice now melts over the summer months, up from 40-50 per cent in the 1990s. Only 10 per cent of the ice survives two years or more.

A separate study last week by the US National Oceanic and Atmospheric Administration and the University of Washington warned that Arctic summers could be completely devoid of ice in 30 years time. Earlier studies forecast that the Arctic ice would vanish only at the turn of the next century.

The polar conference comes on the 50th anniversary of the signing of the Antarctic Treaty. Agreed to by 12 governments, the treaty designated the poles a peaceful "natural reserve" that could not be used by any governments for military purposes.

Clinton said that past agreements on protecting the poles served as a "living example" of governments' ability to cooperate on environmental issues, and urged similar cooperation in the lead-up to a crucial Copenhagen summit on climate change at the end of the year.

"As the world prepares for climate talks in Copenhagen this December, meetings like this are more important than ever," Clinton said. (dpa)