The widow of murdered Belfast solicitor Pat Finucane is to have talks with British Prime Minister David Cameron about the family's demand for a full independent inquiry.
Downing Street is believed to be considering agreeing to some form of investigative tribunal.
However, Geraldine Finucane said they would settle for nothing less than a inquiry which was public, effective and independent.
She is also due to meet the Northern Ireland Secretary of State, Owen Paterson, at the talks in Downing Street next Tuesday.
Mr Paterson said this week that the British government would make an announcement "soon" about the Finucane case, which he described as "complex and difficult".
Mr Finucane was shot as he sat eating a Sunday meal at home. His wife was wounded in the 1989 attack, which was also witnessed by the couple's three children.
There were allegations that some members of the security forces collaborated with loyalist paramilitaries to the extent that they could have stopped the killing.
Retired Canadian judge Peter Cory was appointed by the British and Irish governments to examine allegations of collusion surrounding the Finucane and other controversial killings.
He recommended a public inquiry into Mr Finucane's death, as well as inquiries into the murders of Robert Hamill, a catholic from Portadown, Co Armagh; solicitor Rosemary Nelson and Loyalist Volunteer Force leader Billy Wright, shot dead by republicans at the high-security Maze Prison.
The three other inquiries have already been held.
Loyalist Ken Barrett, 41, was sentenced at Belfast Crown Court to life for Mr Finucane's murder, after admitting his part in the killing.
Mrs Finucane said the family was not prepared to settle for any form of inquiry.
"How the process operates is just as important as the establishment of one," Mrs Finucane said.
"An inquiry that is not public, effective, independent or fully prepared to allow my family to participate to the maximum extent is not an inquiry worth having."
The British government has been seeking a way of dealing with the past which acknowledges the hurt suffered while avoiding lengthy and expensive investigations like the Saville Inquiry into Bloody Sunday.
Mrs Finucane said: "I believe that it is a mistake to ignore cases of serious concern just because they are in the past.
"I believe the only way our society can move forward into a peaceful future is by examining the controversies of our past and exposing them fully for all to see.
"I believe this creates foundations of confidence, upon which lasting peace can be built."