Hawaii’s general-obligation bond rating was cut to Aa2 from Aa1 by Moody’s Investors Service, affecting about $5.1 billion in outstanding debt.

The downgrade to the third-highest ranking reflects Hawaii’s "strained financial operations following the recession-driven fall-off over the last several years," Moody’s analysts Nicole Johnson and Nicholas Samuels said in a report yesterday.

The latest projection for fiscal 2011 revenue is 1.6 percent lower than last year and 8 percent below the recent peak in 2008, the analysts said, reflecting in part the natural disasters in Japan that reduced tourism from that country.

The Moody’s rating change also reflects structural problems related to growing unfunded liabilities in state-run programs that pay pensions and health care benefits for government workers, said Kalbert Young, state budget director.

The rating change won’t have an immediate effect on the state’s finances, but could result in slightly higher borrowing costs the next time the state floats bonds in three to five months, Young said. All other things being equal, a credit rating reduction to Aa2 from Aa1 usually adds about one-tenth to two-tenths of a percentage point to the yield on state bonds, he said. Any premium the state has to pay for the lower rating would be less on shorter maturity bonds and more on those with longer maturities, he said.

Moody’s also will have a chance to reassess Hawaii’s fiscal situation before the bonds are issued, which could result in a higher rating if things improve by then, Young said.