By Lianting Tu and Nethelie Wong

Bank of China has shortlisted eight banks for a planned offshore Basel III-compliant Additional Tier 1 capital offering of up to $6.5 billion, according a source involved in the deal.

Bank of China International is leading the deal, which could be the world's biggest AT1 offering. The Chinese bank has recently hosted a global roadshow for the potential deal, sources said.

The $6.5 billion offering of preference shares could include a $5 billion tranche and a 1 billion tranche, the sources said. BOC could also issue in other currencies. However, preference shares in US dollars and euros would allow the bank to attract more demand and attain better pricing than other currencies, they said.