Trócaire, the Catholic relief agency, has called on the Government to publicly confirm at the earth summit, its commitment to reach the UN target on overseas aid by 2007.
The charity's director, Mr Justin Kilcullen, said the Government should set out a clear "growth path" for achieving this objective, at the international conference on sustainable development in South Africa which starts next Monday.
The world summit on sustainable development, "Rio+10" is a follow-up to the Earth Summit 10 years ago in Rio de Janeiro.
In September 2000 the Taoiseach, Mr Ahern, told world leaders attending the UN millennium summit in New York that Ireland would meet UN targets on aid to the world's poorest countries, 0.7 per cent of Gross National Product by 2007.
Mr Kilcullen said it was important that Mr Ahern "reconfirms in his address to the Johannesburg summit that Ireland will reach the UN target. The Estimates are being prepared for this year's budget. We would like to see Government guarantees on the growth of our overseas budget being reflected in the Estimates."
A Government delegation including the Taoiseach, the Minister for the Environment, Mr Cullen, and the Minister of State for Foreign Affairs, Mr Tom Kitt, and senior civil servants are to attend the summit.