Hillary Clinton: Arctic drilling 'not worth the risk'

U.S. Democratic presidential candidate Hillary Clinton on Tuesday staked out her opposition to Arctic oil exploration, a day after the Obama administration gave Royal Dutch Shell final approval to drill off Alaska.

"The Arctic is a unique treasure," Clinton said in a Twitter post. "Given what we know, it's not worth the risk of drilling."

On Monday, the Obama administration gave Shell final approval to resume drilling into the oil zone off northern Alaska for the first time since 2012.

Shell obtained the leases during the administration of former President George W. Bush.

Arctic drilling is sure to be a contentious issue in the presidential campaign as more Arctic lease sales are scheduled  for 2016 and 2017.

Environmentalists oppose the drilling, saying any spill would harm walruses, whales, and polar bears in a region scientists say is already vulnerable to climate change.

The Arctic contains 20 percent of the world's undiscovered oil and gas, the U.S. government estimates, making it a coveted resource.

Shell suffered a series of mishaps in 2012 in the Arctic, including losing control of an oil rig from which Coast Guard divers dropped from helicopters had to rescue 18 crew members. But the company says Arctic oil, which would not be produced for at least a decade, is needed to meet growing global demand.

On other energy issues, Clinton has sought to balance environmental and economic concerns. Previously she said she would seek to phase out fossil fuel extraction and increase fees on companies operating on public lands in a way that does not disrupt the economy, if she becomes president.

Clinton has been careful not to comment on whether she would approve the Keystone XL oil pipeline from Canada ahead of an expected ruling by President Barack Obama.