Japan's finances are becoming increasingly precarious, Finance Minister Shunichi Suzuki warned Monday, just as markets test whether the central bank can keep interest rates ultralow, allowing the government to service its debt.

Japan's public debt is more than double its annual economic output, by far the heaviest burden in the industrialized world.

The government has been helped by near-zero bond yields, but bond investors have recently sought to break the Bank of Japan's 0.5% cap on the 10-year bond yield as inflation runs at 41-year highs, double the central bank's 2% target.