UPDATE 1-MGM Mirage says CityCenter contractor to file suit

* Liens could seek $492 million

* CityCenter believes actual obligation is much less

LOS ANGELES, March 12 (Reuters) - The primary general contractor for the CityCenter project on the Las Vegas Strip plans to sue the project's owners for $492 million.

MGM Mirage (MGM.N), which owns the multi-tower project in a 50-50 partnership with Dubai World [DBWLD.UL], disclosed the threatened mechanics' lien in a filing to U.S. regulators on Friday.

Officials at Tutor Perini Corp (TPC.N), the lead contractor at CityCenter, did not immediately return a request for comment.

MGM said the actual lien may be filed within 15 days of the notice.

"CityCenter believes that its actual obligation to the general contractor is substantially less than the amount claimed and that it is also entitled to significant offsets against the claimed amount," MGM said in its filing.

The company intends to pursue all of its rights and remedies, including arbitration, but has meanwhile obtained a six-month amendment to its $1.8 billion credit facility that would allow for additional construction liens.

MGM also said it believes it has significant claims against the contractor in connection with construction defects at CityCenter's Harmon Hotel tower. (Reporting by Deena Beasley; editing by Andre Grenon)