Suffolk has achieved the gold standard of public financing — the coveted AAA credit rating.

The Standard and Poor’s rating agency bumped up the city’s credit rating for new and refinanced bonds in a new report issued Tuesday. Similar to an individual’s credit score, credit ratings for municipalities influence the city’s ability to finance projects.

“I’m thrilled,” Mayor Linda T. Johnson said Tuesday. “It’s great for the city. It means a ton, and it means so much to the businesses. It says we’re going to do well, and we’re doing well.”

The city also received a hike of one notch from Moody’s, another rating agency, which upgraded the city’s rating from Aa2 to Aa1, one step below its top rating. Moody’s also assigned a stable outlook, up from no outlook assigned.

The third agency, Fitch, maintained the city’s AA+ rating, one step below its top tier, but upgraded the city’s outlook, from stable to positive.

“The trend of increasing credit ratings since 2008 has saved the city millions of dollars in debt service costs over the life of our bonds through lower interest rates on borrowing costs to finance schools, city facilities, utilities, roadways and the refinancing of old debts,” Johnson was quoted as saying in a Monday press release announcing Fitch’s upgraded outlook.

“This most recent upgrade was in part due to City Council’s continued strong financial practices, responsible choices combined with prudent investments, balanced approach to budgeting and by making the necessary tough choices while still maintaining the high levels of service our citizens deserve and appreciate.”

The new ratings apply to new and refinanced debt the city will take out next week, as well as about $357.6 million in outstanding general obligation bonds.

A team of city officials and employees, which included Johnson, Vice Mayor Charles Brown, Finance Officer Lenora Reid and others, visited the ratings agencies in New York earlier this month. Johnson said the comments were positive.

“I think the comment that we got from all the agencies was that we told them what we were going to do, and we did what we said we were going to do,” she said. “I think it’s that consistency that’s worked so well.”

In announcing its upgraded outlook, Fitch noted the city’s “fiscal discipline supported by prudent budgeting and strong institutionalized policies.” It also said the city’s reserves are robust and its revenue raising capacity is strong and praised the city’s regular cash-funding of capital projects.

Fitch also said the city “adheres to good debt management guidelines, which has allowed overall debt levels to remain moderately low.”

A report from Moody’s that accompanied its upgraded rating noted the city’s “strong and carefully managed financial position with ample general fund reserves” and its sizable tax base. However, it noted an above-average — but manageable — debt burden and warned that an increased debt burden could make the rating go down.