Sources close to the government told the Platts news agency that the budget could rise to JPY 635.9bn ($6.76bn) for the 2013/4 financial year.
The Japanese transport ministry is not commenting.
Japan's crude imports from Iran were only made possible by the introduction at the end of June of a new supplementary insurance framework set up by the Japanese government to get around the EU ban on insuring tankers carrying Iranian oil.
The
