Sinn Féin has launched a discussion document titled 'Towards a United Ireland'.
Speaking at the event, deputy leader Mary Lou McDonald said the party wanted to stimulate debate on the matter.
Sinn Féin MEP Matt Carthy said he would like to see a referendum in the next political term, adding later it could be within two years.
Ms McDonald said every republican would like to see an Irish republic tomorrow.
She said for Northern Ireland’s Secretary of State to trigger a referendum under the terms of the Good Friday Agreement there would first need to be the political will from Dublin.
The document says referendums on Irish reunification would be held concurrently north and south of the border.
It says that the Orange tradition must be accommodated under a new constitution and there would be new symbols and emblems.
On the cost of reunification Mr Carthy said the departments of finance north and south should carry out an analysis.
Northern Ireland Minister for Finance Máirtín Ó Muilleoir said reunification would mean a benefit of £35bn between now and 2025.
The document states that the difference between revenue and actual spending in Northern Ireland is between £2.7bn and £5.1bn.
This figure does not include multinational taxation which is generated in Northern Ireland or paid in Britain.