The Conference of Religious of Ireland (CORI) has called on the IRA to reinstate its ceasefire and on unionists to "hear the legitimate concerns of nationalists".
CORI, which represents more than 15,000 religious sisters, brothers and clergy in Ireland, said it welcomed the decision of the British and Irish governments to set a firm date for all party talks, and the decision that participants would have to show "their absolute commitment to the principles of democracy and non violence".
It added that while republicans needed to take particular steps towards confidence building, "so also do unionists and the British government".
"Many nationalists are deeply concerned about the commitment of the majority of unionists and of the British government to serious negotiations."