The US consul general in Belfast has pledged that the US administration will do what it can to help close a website linked to the Real IRA which bombed Omagh.
Dean Pittman made the announcement after holding hour-long talks with relatives of the 29 people who died in the bombing in August 1998.
Mr Pittman said if there was anything they could do they would do it in support of the families, according to Michael Gallagher, whose son Aidan died in the blast.
Relatives say material posted on the noticeboard of the 32 County Sovereignty Committee site is particularly offensive.
Mr Gallagher told The Irish Times: "It's a shocking website. It's glorifying terrorism and promoting the things we want to move away from in this country. It encourages young people to get involved."
"[ Mr Pittman] said he had already talked to the US embassy in London about the issue and had been asked by London to talk to the families," said Mr Gallagher.
He added: "There was nothing he could guarantee us, except that our allegations about the site would be seriously looked at - and if it is possible to do something, they will do it."
The site is understood to be Canadian-based, according to a reliable source, and therefore not under US jurisdiction. There were also questions of freedom of speech, the source added.
The website noticeboard facilitates discussion of a range of issues and contains references to one of the Omagh dead and to the murder of Ballymena teenager Michael McIlveen.
A US consular office spokesman said Mr Pittman was grateful for the opportunity to learn more about Omagh Support and Self Help Group's endeavours to pursue justice for the victims of the Omagh atrocity. He pledged to discuss with authorities in Washington Mr Gallagher's concerns about the website.