Karen Bradley, the Secretary of State for Culture, Media and Sport, said the date by which Ofcom must report back had been pushed back from 16 May to 20 June.
Ms Bradley said she planned to table a written ministerial statement on the issue early next week.
US entertainment giant 21st Century Fox already has a 39% stake in Sky, the owner of Sky News.
It tabled a proposal just before Christmas to buy the remainder of the business for £11.7bn, valuing the entire company at £18.5bn.
Ms Bradley announced in March that she was intervening in the deal on the grounds of media plurality and broadcasting standards.
The announcement triggered a requirement for media regulator Ofcom to assess and report back on the deal by the initial May deadline - now extended.
A separate review by the European Commission has already given a green light to the takeover.