The successful bidder or bidders for UnitedNetworks' extensive electricity and gas networks will not be known now until probably late September-early October.

UnitedNetworks yesterday said prospective bidders had asked for more time to conduct due diligence. Chief executive Dan Warnock declined to comment on the number or identities of the companies conducting due diligence, but said UnitedNetworks wanted to move pretty quickly on the sale process.

However, industry commentators have recently linked Hong-Kong based CKI, which is to buy Australian electricity distributor Citipower in Victoria for $A1.56 billion, and Singapore Electric as possible bidders for UnitedNetworks.

The Commerce Commission last week cleared Natural Gas Corporation to acquire the gas pipeline assets of UnitedNetworks Limited (UNL) and trust-owned Vector to acquire up to 100% of UNL's shares, as well as some or all of its assets.

Neither NGC nor Vector have expressly stated their intentions regarding UnitedNetworks, with NGC spokesman Keith FitzPatrick saying any decisions to buy or sell assets were likely to be made as part of NGC's overall divestment strategy, which was still being finalised.

NGC last week announced it was getting out of gas retailing and selling its power stations - the 360MW Taranaki Combined Cycle plant at Stratford and its smaller cousin, the 118MW Southdown station in south Auckland, of which NGC owns 50% - and consolidating its role in the New Zealand energy market.

UnitedNetworks parent, American energy company Aquila (formerly the Missouri-based Utilicorp), which owns 70% of UnitedNetworks, wants to sell its Australasian assets to reduce its debt load and please international ratings agencies.