Anadarko Bonds Hurt by Gulf Oil Spill

June 15 (Reuters) - Fitch Ratings on Tuesday changed its outlook on Anadarko Petroleum Corp) to negative, from stable, citing increasing estimates of damages the company is likely to need to pay as a result of the oil spill in the Gulf of Mexico.

A negative outlook indicates the company is more likely to be cut from BBB-minus, the lowest investment grade, over the next one-to-two years. Downgrades into junk territory can significantly increase a company's borrowing costs.

Anadarko owns 25 percent of the oil well that exploded in the Gulf of Mexico in April, causing a massive spill that BP Plc), the largest owner, has struggled to stop.

"Fitch believes that Anadarko will not have to pay punitive damages since it is a non-operating partner; however, it may have to pay its 25 percent share of containment and cleanup costs as well as compensatory economic damages depending on a number of factors," the rating agency said.

Anadarko is expected to have adequate liquidity to fund payments for the spill, which analysts estimate could cost the company around $6 billion, Fitch said. This assumes that punitive damages for BP could rise to around $40 billion.

However, "the negative outlook reflects the potential for containment and cleanup costs as well as compensatory economic damages to greatly exceed these estimates," Fitch said. (Reporting by Karen Btrettell; Editing by Dan Grebler)