BP announced Tuesday it is suspending work on the most critical piece of its $1.5 billion Liberty oil field development in the Beaufort Sea -- a massive drilling rig.

BP said it needs to begin a broad engineering review of the rig to address a number of problems that have arisen during the rig's construction on a man-made island.

"We've gotten to the point that we need to step back, take a time out and make sure that all of these systems, including some critical safety systems, are just like they need to be," said BP spokesman Steve Rinehart.

Previously, BP had expected to begin producing oil from Liberty's first production well next year, but that is "probably not going to happen," Rinehart said.

Liberty is considered one of the most advanced deepwater drilling projects in the world because it requires drilling the world's longest wells -- eight miles long and two miles deep. It's the biggest oil development project under way in Alaska.

But the BP project has been under intense scrutiny since the company's massive oil leak from the Deepwater Horizon rig in the Gulf of Mexico during the spring and summer. Also, the company has been under fire for North Slope spills in the past four years. This fall, a federal lawyer accused the company of violating its federal probation for oil spills on the North Slope tundra.

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