* Anadarko declares force majeure due to drilling halt
* Rigs owned by Transocean, Diamond, Noble Corp-analyst
* Still using one rig for non-drilling activities (Adds names of rig owners, analyst's comment, background)
NEW YORK/SAN FRANCISCO, June 3 (Reuters) - Anadarko Petroleum Corp (APC.N), part owner of the crippled well that has been gushing oil into the Gulf of Mexico since April, said on Thursday it had declared force majeure on three rigs in the region.
"We believe operators have invoked the force majeure clause on a total of four rigs so far, with more expected to come," Sedita wrote in a note to investors on Thursday.
Force majeure relieves a company from liability when it cannot fulfill contractual obligations because of natural and unavoidable catastrophes.
Anadarko said it still had one rig under contract in the Gulf, which it planned to use to continue completion, workover and other non-drilling activities on existing wells during the drilling moratorium issued by the federal government.
The rig kept at work is owned by Ensco Plc (ESV.N), Sedita said.
On June 1, Cobalt International Energy Inc (CIE.N) declared force majeure on another Diamond-owned rig in the Gulf of Mexico. [ID:nSGE6500HH]
Anadarko said it would stick to its full-year and second-quarter sales forecasts and said its spending plans for the year were unchanged.
Anadarko's shares have fallen to $46.06, where they closed on Thursday, from a year high of $75.07 on April 15. (Reporting by Matt Daily in New York and Braden Reddall in San Francisco; Editing by Derek Caney, Toni Reinhold)