The Obama administration approved oil giant Shell’s Arctic drilling program Monday, clearing a major hurdle for the company but inviting the ire of environmentalists concerned over the project's potential contribution to climate change.

The Bureau of Ocean Energy Management gave the green light to the multi-year exploration plan in the Chukchi Sea after reviewing thousands of comments from the public, Alaska Native organizations and state and federal agencies.

The approval came just days before a planned protest of the drilling program in Seattle. Port commissioners are planning to take up the lease issue at a meeting Tuesday.

The Arctic is estimated to contain about 20 percent of the world's undiscovered oil and natural gas, but its recovery could be decades away.

Shell has already spent about $6 billion on exploration in the area. Shell proposes to drill up to six wells in water about 140 feet deep, using two vessels that can serve as relief-wells for each other in case of an emergency.

"We have taken a thoughtful approach to carefully considering potential exploration in the Chukchi Sea," said Abigail Ross Harper, the director of the Bureau of Ocean Energy Management, in a release.

As part of the conditional approval, Shell must obtain permits from the federal government and the state of Alaska in order to begin drilling this summer. Shell has not drilled in the Arctic since a mishap-filled 2012 season, when the company was forced to evacuate its Kulluk drill rig, which eventually ran aground.

One of the vessels that Shell plans to use this summer, the Noble Discoverer, also had problems in the harsh Arctic waters in 2012. At one point it had to be towed to port after experiencing vibrations in a propeller shaft.

Approval from the Obama administration came despite protest from environmental groups concerned about drilling in pristine region with little capacity for emergency response.

"Our government has rushed to approve risky and ill-conceived exploration in one of the most remote and important places on Earth," said Susan Murray, an official at Oceana, a leading voice against Arctic drilling.

Even if Shell gets all the permits it needs, its Arctic aspirations may face a hurdle further south. Last week, the city of Seattle ruled that its port must apply for a permit to allow Shell to make it a hub for drilling rigs headed to the Arctic — thanks largely to Democratic Mayor Ed Murray who is determined to take on climate change.

Activists in Seattle have vowed to stage demonstrations blocking the port with kayaks in protest.

Al Jazeera and Reuters