US Secretary of State Hillary Clinton has called dissident republicans who murdered three members of the security forces in NI this month "criminals".
Mrs Clinton was speaking at a news conference with Irish Foreign Minister Micheál Martin.
A police officer and two soldiers were murdered by dissident republicans in the space of three days in Craigavon and Antrim.
Mrs Clinton said those responsible were a "handful of rejectionists".
She said they were trying "to drag the people of Northern Ireland back into a full cycle of violence and retaliation".
"The recent attacks which killed two British soldiers and a police officer are an affront to the values of every community, every ethnicity, every religion and every nation that seeks peace," she added.
Hillary Clinton has hit out at dissident republicans
Meanwhile, a cross-party delegation from the Northern Ireland Policing Board are in the US for a series of meetings.
Board chairman Sir Desmond Rea said the message they were bringing was "peace and reconciliation is stronger than ever".
The group will meet President Obama and attend St Patrick's Day events.
They will also meet Congress members, the British and Irish ambassadors to Washington and policing representatives.
Sir Desmond said board members would use the visit to send a very clear message to the US administration and the wider Irish American audience of their commitment to "effective, efficient and impartial policing".
He added that they would "reaffirm the unity and resolve that those who would wish to wreck the progress that has been made have no mandate or support within the Northern Ireland community".
"It is clear that, despite the killing of two soldiers and one police officer, the public and political response since is that the message of peace and reconciliation is stronger than ever," he said.
"This visit is being used as a platform to reinforce that message, and to emphasise the unity of the board."
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