Kelly made the comments at the 40th plenary conference of the British-Irish Parliamentary Assembly in County Cavan.
Kelly said that the dissident car bomb that exploded in Newry on Monday night left the North at a crossroads.
"In the past month Northern Ireland found itself at yet another crossroads one of many it has faced in the recent past.”
“The choices it faced were complex as always, but at the end of the day they became very simple, a choice between progression and regression, between moving forward and moving backward, between leaving the past even further behind or allowing it to prevent the region from moving forward," he said.
Kelly added that the U.S. and its government was very happy to see both sides of the political divide work together on issues such as devolution of Justice and the Parades Commission.
“I and the US government and all of you I am sure were very glad to see that the political leaders of Northern Ireland chose the right path yet again, the path that we all believe now leaves Northern Ireland extremely well-positioned to take advantage of the opportunity that lies ahead.
"We now have a clear road map as to how devolution can take place and it is imperative that in the coming weeks we work together in similar fashion to finish the job and complete the task in hand.”
Kelly also demonstrated how the US supported the peace process and acted as a catalyst for change. He also said that Hillary Clinton was the Norths greatest friend and she has vowed to help the North "reap the benefits of peace."
"Successive US administrations and political leaders have supported the peace process and made clear that a lasting peace was a goal worth pursuing, not only to just end hostilities, but because by achieving devolution and a peaceful Northern Ireland, a new economic future could be made possible for all of the citizens of Northern Ireland.
“Be assured that Northern Ireland has no greater friend than secretary of state Hillary Clinton, who has been committed to helping the peace process through an economic platform. Her belief that peace and prosperity work hand-in-hand led to her decision to appoint me as economic envoy,” said Kelly.
“Her belief is that peace and prosperity work hand-in-hand. She has vowed that the US will continue to help Northern Ireland reap the dividends of peace."