The siblings were chosen by the Tipperary International Peace Award for their reconciliation work in Northern Ireland and across the world.

Senator Kennedy, who died in August aged 77, and 81-year-old Mrs Kennedy Smith join an impressive list of previous winners, including Nelson Mandela, Bill Clinton and Sir Bob Geldof.

Announcing the award, organisers paid tribute to the Boston-born pair.

"Senator Edward Kennedy is being honoured for his courageous leadership for peace, human rights, and nuclear disarmament," a statement said.

"Jean Kennedy Smith is being honoured for all she did to enable future generations, regardless of their background, to share in Ireland's promising future."

A spokesman for the prize said he hoped Mrs Kennedy Smith would attend the formal presentation ceremony in Ballykisteen, Co Tipperary later this year.

The last surviving child of Rose and Joseph Kennedy, Mrs Kennedy Smith spent five years as US Ambassador to Ireland after being nominated by President Clinton in 1993.

Her younger brother Ted, a senator for his home state of Massachusetts for more than 46 years, was intricately involved in Northern Irish politics during and beyond the Good Friday agreement.

He was also a keen campaigner for nuclear disarmament and long supported the abolition of nuclear weapons.