Plans to take BBC Three off-air could be confirmed today when the BBC Trust announces its final decision.
A proposal to move BBC Three online was provisionally approved by the Trust in June, but it sought a series of assurances from the broadcaster ahead of today.
BBC Three has been home to shows including Gavin And Stacey, Sun, Sex and Suspicious Parents, and Don't Tell the Bride.
The BBC Executive wanted BBC Three to move online to cut costs, and in its provisional conclusions, the Trust said that it had some ''clear concerns'' about the short-term impact of the change, including ''a potential impact on the ability of the BBC to try out new ideas and develop new talent''.
In the short term the online channel would be likely to lose viewers, having a ''much smaller audience than the broadcast channel it is replacing''.
But it said that the plans should be approved, as the online service would save £30 million a year and be more distinctive than the current BBC Three channel, whose audience is falling.
It said that the move should be dependent only on the Executive agreeing to several conditions, including clearer commitments to shows on BBC One and/or BBC Two which appeal to younger audiences.
The announcement was bad news for campaigners who have battled to keep BBC Three alive as a TV channel and have called the move ''disastrous'' for the fostering of ''new talent'' and ''innovative ideas''.
More than 300,000 people have signed a petition to save the channel on change.org.
Jono Read from the #SaveBBC3 campaign said: "If the BBC Trust is truly there to represent the viewer, on Thursday it will reject proposals from the BBC to make BBC Three an 'online-only' service.
"So far both the BBC and BBC Trust has failed to listen. The voice of the majority is in favour of keeping it on television. From the 300,000+ names on our petition to the BBC Trust's own polling and consultations.
"They all point to wanting this channel on television. Any other decision from the BBC Trust would show disregard for the people who pay the licence fee."
Harry Potter star Daniel Radcliffe, Broadchurch actress Olivia Colman and Poldark's Aidan Turner are among those who have signed an open letter on the issue.
Jimmy Mulville, who runs production company Hat-Trick, which is behind hit shows including Room 101, Father Ted and Have I Got News For You, has said the proposed move online would be ''the kiss of death'' for the channel and leave it ''competing with huge behemoths like Netflix and Amazon who are spending hundreds of millions of dollars on one show''.
The Executive originally said that plans to move BBC Three online, as a service targeted at 16- to 34-year-olds, would save £50 million a year, but the Trust said that it had taken other costs into account to bring the figure down to £30 million.
The BBC wants to use savings from the closure of the BBC Three channel to invest in drama on BBC One.
BBC Three supporters have been hoping to follow in the footsteps of campaigners who successfully saved BBC 6 Music from closure in 2010.
The Trust will also announce its final decision on BBC One Plus One, iPlayer and CBBC.
The body provisionally rejected proposals for a BBC One plus one channel in June, saying a plus one channel would be at the expense of commercial rivals and reduce the profitability of ITV and Channel 5.
It accepted the proposal for iPlayer to become more than a catch-up service, by hosting live content as well as carefully selected third-party content, and it also provisionally accepted the proposed extension of CBBC hours.