ASIAN banks including DBS Group have been invited to help underwrite Prudential's US$20 billion (S$28 billion) rights issue, sources with knowledge of the deal told Reuters on Tuesday.

The move suggests that Prudential's main bankers, Credit Suisse, HSBC and JP Morgan could reach out to Asian investors if the rights are not fully taken up, sources said.

"Asian banks have been invited to underwrite the Prudential share issue," one of the sources with knowledge of the deal said. "The banks here are the ones who have the liquidity."

Big rights issues, such as the US$18 billion deal by HSBC itself a year ago, usually involve multi-layered bank syndicates, with bookrunners and sub-underwriters sharing the risk that part of the equity is left unsold.

The Government of Singapore Investment Corp (GIC), the city-state's biggest sovereign wealth fund, has a 0.5 per cent stake in Prudential, one of the few large Asian institutional investors with a stake in the British insurer.

Singapore's DBS, Southeast Asia's biggest lender, is among the banks invited to underwrite the deal, a second source said. Last year, DBS underwrote more than US$2 billion of equity issuance. A DBS spokeswoman declined to comment.

A GIC spokeswoman declined to say if they would participate in the rights offering.

Prudential is conducting the rights issue, the largest share offering in UK history, to part-finance its US$35.5 billion acquisition of AIG's Asian unit.