NEWYORK (Bloomberg) Swiss Reinsurance Co., the world's second-largest reinsurer, had its credit ratings cut by Moody's Investors Service on concern that prices for some policies may have peaked.

Moody's lowered Swiss Re's senior debt and financial strength ratings to Aa2, the third-highest level, from Aa1. The insurer lost its Aaa rating, the highest possible, in 2002 due to losses from stock market investments, the September 11 terrorist attacks and policies sold too cheaply in previous years.

Falling prices for property and casualty reinsurance, low investment yields and potential reserve shortfalls may crimp Swiss Re's ability to generate profit, Moody's said in a statement.

The insurer will "be challenged to further improve the quality and sustainability of earnings," Moody's said. The outlook for Swiss Re's ratings is stable, it said.

The downgrade widens the gap between Warren Buffett's Berkshire Hathaway Inc., the only reinsurer with an Aaa rating, and other large reinsurers. The credit rating of Munich Re, the world's largest insurer, has fallen three levels in two years.

"Swiss Re has a stable ratings outlook from all three rating agents and continues to be one of the highest rated reinsurers worldwide," Swiss Re spokesman Michael McNamara said. "Swiss Re is committed to maintaining its top-ranked financial strength and rebuilding its capital base through future earnings."