Japan's deteriorating public finances have prompted Standard & Poor's to cut its sovereign debt rating, but experts say the move has had little negative impact and could even help the government persuade the public to accept reforms that might result in a tax hike.

The U.S. rating agency on Thursday downgraded Japanese long-term debt for the first time since 2002, knocking it down a notch to AA- from AA. This put it in the same group as China but below Spain, which is being threatened by the sovereign debt crisis in Europe.

S&P cited the lack of a "coherent strategy" by the government of Prime Minister Naoto Kan to restore Japan's finances, which are ranked the worst among major developed countries because the combined debt of the central and regional governments is nearly 200 percent of gross domestic product.