APA Group's acceptance of a $13 billion cash takeover bid from Hong Kong-based CK Infrastructure Holdings has done little to address investor worries about regulatory approvals while signalling that the target's talks with other "admirers" has failed to elicit a higher offer.

Chairman of the gas pipeline owner, Michael Fraser, said on Monday that the APA board was "satisfied with [CKI's] prospects of obtaining clearance" from the competition and foreign investment regulators.