A chairman has been appointed to lead a convention to prepare the way for a referendum on establishing a full law-making parliament for Wales.
Sir Emyr retired from his UN post in July
First Minister Rhodri Morgan and his deputy Ieuan Wyn Jones announced that former UK ambassador to the UN Sir Emyr Jones Parry, 60, was taking on the job.
Plans for a referendum within four years were key to the deal to form a Labour-Plaid assembly government.
Mr Morgan said the poll would be "on or before the next (assembly) election".
"I am delighted to be asked to serve as chair of the All-Wales Convention, and I am looking forward to starting work," Sir Emyr said.
Mr Morgan said Sir Emyr "commands enormous public respect but has those fine, fingertip diplomatic skills which will no doubt be called upon to establish and run the convention".
He also emphasised that Sir Emyr would not be involved in a campaign for a yes vote.
"In terms of the period of building a convention, taking evidence, exploring how to engage with civil society throughout Wales, I think everybody will agree that you couldn't have anybody finer than Sir Emyr Jones Parry," said Mr Morgan.
The Welsh assembly's law-making powers were increased this year as a result of the 2006 Government of Wales Act.
It allows for primary legislative powers after a referendum.