The source told Bloomberg that Prudential hopes the extra money will mean the Financial Services Authority in the UK gives its approval to the deal.
Last week, Prudential put back a planned $21 billion rights offering after the British regulatory body asked the firm to increase its capital levels.
Prudential also needs the approval of three-quarters of its investors for the AIG deal to go through.
Earlier this year, AIG and Prudential provisionally agreed that the takeover would take place for a fee of $35.5 billion.
AIG intends to use the money raised from the agreement to help repay some of its debt owed to the Federal Reserve Bank of New York.
By Asim Shah