Britain's Prudential Plc
plans to do a rights offering of about $20 billion to finance a $35.5 billion purchase of American International Group's Asian life insurance unit, a source familiar with the situation said on Sunday.

Prudential's rights offering will be backstopped by Credit Suisse , HSBC and JPMorgan Chase , the source said, declining to be named because the deal is not yet public.

Prudential plans to pay about $10.5 billion of the purchase price in equity, and that would include about $5.5 billion in common stock, the source said.

AIG was advised by Citigroup and Goldman Sachs , while its board was advised by Blackstone Group , the source said. Credit Suisse, Lazard Ltd , JPMorgan and HSBC advised Prudential, the source said.

(Reporting by Paritosh Bansal; Editing by Diane Craft)