Sinn Féin is under fresh US pressure to explain the arrests of three Irishmen in Colombia.
Mr George W Bush's adviser on Northern Ireland, Mr Richard Haass, has signalled he would be seeking an explanation from Sinn Féin this week.
His comments came after talks with Northern Secretary Mr John Reid in London.
Mr Haass said: "The United States, as you all know, has important national interests in Colombia.
"We have got hundreds of Americans on the ground there. We have put in hundreds of millions of dollars of aid to help that country battle the insurrection, drug trafficking and so forth.
"Colombia is a major country in the western hemisphere. It is very important economically.
"So any co-operation with people in Colombia who are challenging the law, promoting the sale of drugs, is to the US extremely, extremely disturbing. My concerns about those contacts are real."
President Bush's administration and several leading Irish American politicians have been alarmed at the arrests of James Monaghan, Niall Connolly and Martin McAuley last month on suspicion of training members of the left-wing FARC militia, as well as travelling on false passports.
The three men have been detained in a high security prison as the Colombian authorities investigate their activities.
PA