LONDON (Bloomberg) — The UK's sovereign credit rating is most at risk among top-rated nations, Fitch Ratings said, citing concern over the country's budget deficit.

The rating faces risks because the UK needs "the largest budget adjustment", David Riley, head of global sovereign ratings at Fitch, said in an e-mailed statement. "Our stable rating outlook reflected our expectation that the UK government will articulate a stronger fiscal consolidation programme next year."

Britain last month reported the biggest budget deficit for any September since records began in 1993 as the recession ravaged tax revenue and drove up welfare costs. The £14.8 billion ($24.7 billion) shortfall compared with a deficit of £8.7 billion a year earlier, the Office for National Statistics said in London on October 20.

"Many credit profiles of major 'AAA' sovereigns have been significantly weakened by the financial crisis and the subsequent recession," Riley said in a separate statement. "The already out-sized budget deficits and the rise in government debt had reduced the 'fiscal space' for policy makers to respond to further adverse shocks."

The US's rating also might be at risk of a review if its fiscal position does not stabilise in the next couple of years, Riley was reported by Reuters as saying in a television interview.

Standard & Poor's lowered the outlook on the UK's AAA rating to "negative" from "stable" on May 21, citing the country's rising debt burden.

"We have assured people that we're taking the necessary action to cut the deficit in half," Prime Minister Gordon Brown told a regular press conference in London. "Our debt levels are roughly the same when this crisis ends as America, as France, as Germany."

Greece's credit rating was cut one step to A- by Fitch Ratings on October 22 after the country increased estimates for its budget deficit. The outlook is "negative", meaning the next move is more likely to be lower.