US envoy to Northern Ireland Mitchell Reiss has warned a congressional hearing that the US made the wrong decision if it denied a travel visa to a Sinn Féin representative for political reasons.
Asked by a congressman about the recent State Department decision not to grant a travel visa to Sinn Féin's US representative Rita O'Hare, Mr Reiss said he has already told government agencies that the visa denial should be "once off" and was "bad policy" if it was done for political reasons.
He praised Ms O'Hare's work as "interlocutor to Sinn Féin", and said he hoped she would be able to continue doing her job.
Mr Reiss made his comments before the International Relations Committee which was sitting to hear an update on Northern Ireland politics.
His statement followed a question by New York congressman Eliot Engel, who said that denying Ms O'Hare a visa made no sense, and that he wanted to register his "extreme displeasure".
Last week it emerged that Ms O'Hare was temporarily denied a visa after she applied to travel to Florida to visit US businessman and Northern Ireland peace advocate Bill Flynn.
Mr Reiss said there were restraints on his ability to answer a question about an individual visa decision, but said it was "bad policy" to deny Ms O'Hare a visa for policy reasons. He hoped it would not become a precedent.
Mr Reiss also told the hearing that there was a "culture of criminality" in some Republican areas of the North, and this had led to threats against the sisters of murder victim Robert McCartney, who was killed by alleged IRA members in January.
His comments were in response to New York Congressman Peter King, who said the IRA did not sanction the murder but its members may have been involved in a cover-up.
Mr Reiss said the McCartney sisters had told him they were warned that they would be burned out of their apartment and had been harassed on the street because they had led a campaign to seek justice for Robert McCartney.
They had also told him they believed that Sinn Féin had lost to the SDLP in Short Strand in the recent election because of their campaign.
Congressman King added that the killing was a pub dispute that could have happened in any city in the US.