The deal, which would see the transatlantic telecommunications giants joining forces to develop an international Internet protocol, is being investigated for possible security threats it is reported.
A spokesman for BT had no knowledge of the investigation but denied it posed any risk to security. "It is just a big network. It is scheduled for completion and regulatory approval this autumn and that is still the case," he said.
AT&T was also staying tight-lipped on the issue. "As far as we are concerned we are on track to get FCC (Federal Communications Commission) approval," a spokeswoman said.