AT&T announced it plans to buy Time Warner on Saturday for $85.4 billion
Kaine said lawmakers and regulators have to review the deal and "get to the bottom" of questions over whether the merger would decrease competition
The biggest deal in the world this year will give AT&T control of HBO and CNN, Warner Bros and other coveted media assets
Even before the announcement, US consumer groups called for regulators to consider the impact of the tie-up
The two firms have reached an in-principle deal for about $85 billion
Citing people familiar with it, WSJ says that deal would create a new hallmark in the fast-converging media, communications and Internet industries
The talks, which at this stage are informal, have focused on building relations between the companies rather than establishing the terms of a specific transaction