The top sovereign credit ratings of Britain and the United States are not under threat of a downgrade right now, but a worst case scenario foresees a cut by 2013, analysts from Moody's Investors Service said.

The comments, which reiterated an analysis from the ratings agency released last week helped to lift the pound to session highs.

"Only the UK and the US are classified as 'resilient,' rather than 'resistant.' Their resiliency will be tested in the next couple of years, but for now they have a high degree of finance ability and debt affordability," the analysts said in a presentation.

"The rise in debt and higher interest costs could test the ratings under some scenarios, but not right away."

The analysts said they did not expect either country to lose its "AAA" rating but two risks to this view are how quickly interest rates rise over the next few years and debt finance ability.

This is the ability of a government to raise a large amount of debt in its own currency without paying punitive rates.

Sovereign credit risk has become a sensitive issue for investors this week after Standard & Poor's cuts its sovereign credit rating outlook of Spain and Fitch downgraded Greece's debt rating.