Transocean Ltd. said Friday that insurers of its sunken Deepwater Horizon drilling rig have asked a federal judge to decide if BP Plc and other owners of the Macondo well are entitled to any insurance coverage for the April 20, 2010 disaster.

Transocean said it, and its underwriters, believe that BP and minority well owners Anadarko Petroleum Co. and Mitsui & Co. Ltd. are not entitled to any of its insurance proceeds for the BP disaster. But the company, owner of the world's largest offshore drilling fleet, said that court filings made Friday risk proceeds Transocean has previously listed on financial statements as assets.

"Ultimately, these actions may limit the amount of insurance coverage otherwise available to us and may have a material adverse effect on our statement of financial position, results of operations or cash flows," Transocean said in a securities filing.

Transocean owned the Deepwater Horizon, which was drilling BP's Macondo Well in the Gulf of Mexico when it exploded and sank, killing 11 and touching off the worst marine oil spill in U.S. history.

Soon after the disaster BP and the other well owners told Transocean's insurers that they would seek coverage under the policies, which provide liability coverage up to $950 million, Transocean said.The insurers who requested a judicial opinion Friday wrote liability coverage for the Deepwater Horizon totaling $150 million, Transocean also said.

In a statement late Friday, Transocean made clear that it "does not believe that BP will be awarded a significant amount of insurance claims under our excess liability policy" and that its insurers took the matter to New Orleans' federal court "to ensure that their payments do not exceed the limit of liability stated in the policy."  BP did not immediately comment.

In recent financial statement Transocean reported assets of $180 million related to insurance policies for Macondo-related costs and losses.

Transocean said Friday that it is evaluating the impact that Friday's court filings could have on that amount, though "there can be no assurance that we will receive any such proceeds from the court or that insurers subscribing to additional layers of our $950 million excess liability policies will not file similar interpleader actions."