American International Group Inc
The move is consistent with Benmosche's plan to rebuild AIG, as Chartis is seen as core to the insurer, the source said.
AIG, which the U.S. government had to prop up with $180 billion in taxpayer funds, had earlier planned to sell a stake of up to 20 percent in Chartis through either an initial public offering or transactions with private investors.
The company renamed the unit as Chartis in July.
But a Chartis initial public offering was still some time away. That IPO was seen as third in line, after AIG's American International Assurance and American Life Insurance Co life insurance units, the source said.
The insurer is still working on its IPO plans for those two units, the source said.
Benmosche, who this summer became the fourth person to take over as AIG CEO since June 2008, has slowed down divestitures as he oversees a broad restructuring to pay back the government.
Last month, AIG posted its second straight quarterly profit, helped by a recovery in the value of its investments, although its underlying business remained weak.
AIG declined to comment. The source requested anonymity because the discussions about Chartis are not public.
Shares of AIG were up 4.9 percent at $29.42 in morning New York Stock Exchange trading.
(Reporting by Paritosh Bansal; Editing by Lisa Von Ahn)