The family of Belfast murder victim Robert McCartney will be invited to President George W Bush's St Patrick's Day reception, the BBC has learned.
Robert McCartney, 33, was killed near Belfast city centre
The US government is not inviting local politicians to the White House party, but is focusing attention on figures it believes are acting as peacemakers.
Mr McCartney, 33, was murdered on 30 January after a row in a bar. His family claim republicans were involved.
Mr McCartney's sister, Paula, said they would use the invite to get justice.
"Our message will be to highlight the murder of our brother Robert. We will be asking him to support us in our campaign for justice and indeed for justice for Ireland," she said.
In recent days, the IRA has expelled three members over the father-of-two's murder, following an "internal investigation", and Sinn Fein has suspended seven members suspected of involvement.
Robert McCartney's sisters attended the Sinn Fein conference
At the weekend, family members attended Sinn Fein's annual conference in Dublin.
In an address to delegates, Mr Adams said the killing was dreadful and the alleged involvement of some republicans made it a huge issue for Sinn Fein.
"As president of Sinn Fein or as an individual, I could not campaign for the victims of British or unionist paramilitary thuggery, if I was not as clear and as committed to justice for the McCartney family," he said.
Mr McCartney's sister Catherine said they were encouraged by Mr Adams' speech but their only concern was to see the perpetrators in court.
All five of Mr McCartney's sisters, and his partner Bridgeen, are going to Washington.