NEW YORK - December 8, 2009 - Moody’s Investors Service said its top debt ratings on the U.S. and the UK may test the Aaa boundaries because their public finances are worsening in the wake of the global financial crisis.

The U.S. and U.K. have resilient Aaa ratings, as opposed to the resistant top ratings of Canada, Germany and France, analysts led by Pierre Cailleteau in London said in a report. None of the top-rated countries is vulnerable, or have public finances that are stretched beyond the point of no return to the Aaa category, New York-based Moody’s said.

The dollar weakened to 88.60 yen, from 89.51 yen, and strengthened to $1.4795 per euro from $1.4827. The pound fell against all 16 most-traded counterparts, dropping to $1.6289, from $1.6446. It weakened to 90.83 pence per euro, from 90.16. U.K. bonds rose, pushing the yield down 8 basis points to 1.08%, the biggest drop since November 9.

“There has been a huge increase in debt-to-gross-domestic-product ratios as a result of the crisis,” said David Keeble, head of fixed-income strategy in London at Calyon, the investment-banking unit of Credit Agricole SA. “It’s right that there should be a lot of attention and pressure on these numbers.”