Commonwealth Bank of Australia, which owns ASB in New Zealand, says it has begun discussions to buy BankWest in Western Australia from Halifax Bank of Scotland, which is itself being taken over by Lloyds TSB.

Previous reports have said CBA is likely to pay around A$2 billion for the bank.

"Commonwealth Bank has commenced exclusive negotiations with HBOS plc for the acquisition of BankWest," the bank said in a statement before the market opened in Australia.

"Whilst discussions are continuing, the parties have not reached agreement."

There was no comment about whether CBA would buy HBOS' Sydney-based property financing arm, BOS International, which has reportedly lent NZ$3 billion to New Zealand finance companies and property developers in the last three years. Most expect it will not be sold to CBA and may have to find a buyer elsewhere or be closed.