The attorney general has written to the mother of Hillsborough victim Kevin Williams to say he cannot fast-track a new inquest into her son's death.
Anne Williams had hoped Dominic Grieve would be able to bring the inquest forward, after he vowed to help on learning she had terminal cancer.
He has told her he will apply to the High Court for a new inquest as soon as possible.
But he added the timing of when it would be held is outside his control.
Mrs Williams, 59, from Chester, said she was not surprised by the attorney general's decision as her solicitor had already warned her it might be the case.
Kevin was 15 when he died in the disaster at the Sheffield stadium on 15 April 1989.
The original inquest in 1991 returned a verdict of accidental death, ruling that all the victims were dead by 15:15.
Mrs Williams said she had evidence that he was still alive at 16:00 on the day of the disaster and has always campaigned for a fresh inquest, through her charity Hope For Hillsborough (For Justice).
Mr Grieve applied to quash the original verdicts of Kevin and the 95 others who died in the tragedy, after new evidence emerged in the Hillsborough Independent Panel's report.
Last month, an online petition was set up calling for a new inquest to be held for Kevin as soon as possible after Mrs Williams was diagnosed with bowel cancer.
So far it has been signed by more than 30,000 people.
The office of Mr Grieve responded by posting a note on the petition, saying he would give the matter priority.
He has now written to Mrs Williams personally, saying he cannot fast-track her case.
A statement from his office said he was "deeply saddened" to hear of Mrs Williams' diagnosis.
It read: "He has written to Mrs Williams saying that he will make the application for a fresh inquest as soon as he can. This work is being given the highest priority.
"If that application is successful, the timing of any inquests is outside his control. That is a matter for the coronial process.
"He has considered whether he could make the application sooner if he dealt with Kevin's death only, with a later application for the other deaths.
"Unfortunately given that all the deaths arose from a single chain of events and so much of the evidence applies to all the cases, he does not think that is possible."
Mrs Williams said she would have loved to have been in court for the new inquest, but is not sure how long she has left to live.
"I'll be straight, I don't know how long I've got," she said.
"I tracked all the witnesses down and they have been bullied, they have had their statements changed, nobody believed them about Kevin.
"It would have been lovely to sit in court and to hear these people tell the jury exactly what happened to my son."
She has thanked everyone who has supported her campaign.