WASHINGTON (AP) — The Obama administration's approval of drilling for oil in the Arctic Ocean clashes with the message President Barack Obama will deliver when he visits Alaska to emphasize the dangers of climate change, some environmental groups say.

As much as the groups praise Obama for his overall body of work — from stricter fuel-efficiency standards to regulations aimed at reducing greenhouse gas emissions from power plants — they consider the approval of exploratory drilling in the Arctic a stain on his environmental legacy that will send a mixed message to other countries about the seriousness of confronting global warming.

The burning of fossil fuels causes more greenhouse gases to build up in the atmosphere. Some groups would prefer leaving the oil in the ground and not tempting the harsh environmental conditions that could hinder the response to any potential spill.

"It sends a terrible signal to the rest of the world for the United States to be using public resources to promote that development," said Niel Lawrence of the Natural Resources Defense Council. "We have to make clear to the rest of the world that we are all in on a clean energy future. And we've got to stop giving the rest of the world license to go exploring by permitting Shell to do it."

The administration previously allowed Royal Dutch Shell to begin drilling only the top sections of two wells in the Chukchi Sea because key equipment, called a capping stack, was stuck on a vessel that needed repair in Portland, Oregon. Now, Shell is free to drill into oil-bearing rock, estimated at 8,000 feet below the ocean floor.

The U.S. Geological Survey estimates that U.S. Arctic waters hold 26 billion barrels of recoverable oil. Shell is eager to explore in a basin that company officials say could be a "game changer" for domestic production.

Obama, who is scheduled to visit Alaska later this month, says he is mindful of the dangers of offshore drilling, particularly given the 2010 Deepwater Horizon oil spill.

"When it can be done safely and appropriately, U.S. production of oil and natural gas is important," he said at a news conference earlier this year. "I would rather us, with all the safeguards and standards that we have, be producing our oil and gas, rather than importing it, which is bad for our people, but is also potentially purchased from places that have much lower environmental standards than we do."

When asked whether the administration was sending contradictory messages, White House spokesman Frank Benenati said the administration has invested heavily in renewable energy so that the nation can transition off fossil fuels.

"But it's also true that we cannot make that transition overnight, which is why we have taken steps to ensure safe and responsible development of our domestic energy resources that benefits our economy and enhances global energy security, with safety remaining paramount," Benenati said.

Democratic presidential candidate Hillary Rodham Clinton made clear on her Twitter account Tuesday that she disagrees with Obama.

"The Arctic is a unique treasure. Given what we know, it's not worth the risk of drilling," she wrote.

The administration's approval of Shell's exploration efforts has done little to stem criticism from congressional Republicans and industry officials who have often accused it of hindering oil and gas production on federal lands. At the same time, the go-ahead has upset a key base of his support.

"It's perplexing and depressing, quite frankly, to hear President Obama say he wants to fix climate change but then approve Arctic drilling. It's like a doctor diagnosing a patient but then refusing to write a prescription," said Rebecca Noblin, Alaska director for the Center for Biological Diversity.

Lawrence prefaced his criticism of the go-ahead to Shell by saying Obama has done more to fight climate change than "any other leader in world history."

In his visit to Alaska, Obama is expected to stress the dangers of climate change. He says Alaskans are on the front lines of the problem.

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Associated Press writer Dan Joling in Anchorage, Alaska, contributed to this report.