Members of the Ulster Unionist Party, Northern Ireland’s largest political group and a reluctant player in the peace process, elected a hard-liner Friday as their new leader.

David Trimble’s election was a surprise - and a sharp rebuke to efforts to resolve conflicts over Northern Ireland’s future. His leadership threatens the start of peace negotiations and could bar the participation of Irish Republican Army supporters.

“I am sure this party will unite and meet the challenges that lie before us,” he said. “That challenge is to ensure that our democratic birthright as British citizens within the U.K. is recovered and preserved for ourselves and for the future.”

Trimble, 50, has a sharp analytical mind but can be acerbic and impetuous. He has been a member of the British Parliament for just five years, and was viewed as the least experienced candidate.

He emphasized he would have nothing to do with the IRA-allied Sinn Fein party as long as the IRA retains its weaponry.