MGM grand expecting rating upgrade.

Moody’s Investors Service put its ratings on MGM Mirage (MGM) on review for possible upgrade after the casino operator said it is trying to extend the maturity dates on $5.55 billion of credit lines to 2014 from next year.

Moody’s vice president Peggy Holloway said an extension “would be a positive step forward for MGM with respect to near-term financial flexibility as well as its longer-term ability to remain viable as a going concern.” The proposed amendment also would allow the company to issue more secured debt, which could be used to refinance other borrowings.

Moody’s–which rates MGM at Caa2, or two steps into highly speculative territory–said any upgrade likely would be modest because of the company’s high leverage, challenging operating environment and possible difficulty in closing condominium sales at CityCenter, its recently opened hotel-retail-and-condo development on the Las Vegas Strip.

Among the issues the rating agency will consider in its review are specific terms of MGM’s amendment, the operating environment in Las Vegas, the potential sale of the company’s interest in the Borgata casino in Atlantic City, N.J., and its possible initial public offering in Macau.

In November, MGM said it swung to a third-quarter loss as it took a $1.17 billion write-down on its $8.5 billion CityCenter project, but Chairman and Chief Executive Jim Murren said results continued to improve from earlier in the year.