US President Barack Obama has delivered a rousing speech at College Green in Dublin, ending with a translation of his famous campaign slogan 'Yes we can'.
"Is feidir linn," he said, was the correct response when faced with doubters who believed dreams could not be achieved, or current difficulties overcome.
Earlier, another Irish phrase drew huge cheers. "Ta áthas orm le bheith in Eireann (I'm happy to be in Ireland)," he said.
He said he wished somebody had traced his Irish roots when he was a politician in Chicago, which he dubbed the Irish capital of the mid-west.
He revealed he craved a slot in the local St Patrick’s Day parade, only to be given the final place ahead of the street cleaners.
“I bet those parade organisers are watching TV today and feeling kind of bad because this is a parade right here,” he said.
The president visited his ancestral homeland in Monegall, Co Offaly earlier and entertained distant relatives as they enjoyed a drink in a local bar in Moneygall.
He said: “I feel even more at home after that pint that I had. I feel even warmer.”
The president praised the work involved in achieving peace in the North.
“America will stand by you always in your pursuit of peace,” he said. “Ireland, you need to understand that you have already passed the world’s highest hopes.”
He added: “A dream has turned to a reality because of the work of this nation.”
The president met the North's First Minister Peter Robinson and Deputy First Minister Martin McGuinness before making the speech.
In a resounding address, the president said: “This little country that inspired the biggest things – your best days are still ahead of you.”
The president said the US and Ireland had a centuries-old relationship.
“And that’s why I can come here today, as American president, and reaffirm these bonds of affection,” he said.
After a 24-minute speech, the president went down from the stage and shook hands and chatted with well-wishers lucky enough to be at the front of the massive crowds.