Ratings agency Standard & Poors on Monday reaffirmed the ACT's rating.

However, the agency said there was a negative outlook.

There was at least a one-in-three chance the ACT would underperform S&P's forecasts, which suggests the ACT's cash operating balance could revert to a small surplus in coming years.

"ACT's economic fundamentals remain very strong, despite a sharp contraction in the third quarter of 2021," S&P said.

"ACT has a very high-income economy, reflecting its location as home of the Commonwealth government and the Australian Public Service."

The ACT was the only Australian jurisdiction to retain this rating.

However, the Commonwealth government also has the prestigious rating. Should the Commonwealth lose this the territory would also lose its AAA rating.

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Chief Minister Andrew Barr said the rating was due to strong economic management.

"The decision from the credit rating agency recognises the ACT's strong economic management and recovery plans during one of the biggest economic shocks in our city's history," Mr Barr said.

"We injected much-needed support into our economy to protect jobs, support our most vulnerable and invest in a pipeline of sustainable city-shaping infrastructure."

The ACT's recent lockdown contributed to a near-$1 billion deficit in the territory's budget. The budget forecast the deficit would remain until at least the 2024-2025 financial year.

Mr Barr has previously said the ACT's economic recovery would be underpinned by a surge in consumer spending over the Christmas and summer period.

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