Moody's Investors Service cut its rating on Japan's government debt by one notch to Aa3 on Wednesday, blaming a build-up of debt since the 2009 global recession and revolving-door political leadership that has hampered effective economic strategies.

Japan is preparing to elect its sixth leader in five years to replace unpopular Prime Minister Naoto Kan, under fire for his handling of the response to a March tsunami and subsequent radiation crisis at a crippled nuclear power plant.

The downgrade, while not out of the blue, served as another reminder of the debt burdens that nearly all of the world's major advanced economies shoulder, even as policymakers struggle to agree on ways to stimulate sub-par growth without massive new spending.

Moody's new rating on Japan's debt is three notches below coveted AAA status, which Tokyo lost in 1998, but is still classified as high grade.

Japan is now the same level as China, which surpassed it last year to become the world's second-largest economy.-Reuters