It is understood that BNP Paribasand Commerzbankare well placed to win the joint mandate to lead the debut Eurobond, which will have a minimum size of $300 million with maturity of five-seven years. It will be open to international subscribers outside the US.

The central bank is expected to make a decision soon on whether to give the green light to Fitch to issue a sovereign credit rating. It is understood that the agency has completed its evaluation process and is in a position to publish a rating right away. Bankers say the rating is likely to come ahead of the bond issue, but do not consider it a precondition for a successful deal. 'I believe there is an investor base that would buy the paper even without a rating,' says one European banker.

The only agency that currently rates Iran is US-based Moody's Investors Service, which maintains a sub-investment-grade B2 rating. The outlook on the rating is positive due to Iran's strong macroeconomic performance in the past two years.