Sinn Fein President Gerry Adams, right, and party colleague Martin McGuinness, left, arrive for a press conference in West Belfast, Northern Ireland in 2005. File picture: Peter Morrison/AP

London - Sinn Fein leader Gerry Adams is set to be replaced by his deputy, Mary Lou McDonald, on Saturday after nearly 35 years at the head of the Irish republican party.

The 69-year-old veteran of his party's struggle to end the partition of Ireland announced in November that he planned to hand over power at a special meeting of members.

"Leadership means knowing when it is time for change and that time is now," Adams said as he made the announcement.

McDonald, 48, has urged Sinn Fein members to help her "build a new Ireland."

"Uniting this island is the best outcome for all our citizens and it is now our task to convince our unionist friends and neighbours of that and to encourage them to help us build a new Ireland," she said as she accepted the party's nomination to succeed Adams.

Speaking last month, Adams said his decision to step down was "part of Sinn Fein's 10-year plan for the regeneration and renewal of the party."

He warned that sectarian politics in Northern Ireland had again become "very polarized at this time and the atmosphere is very toxic."