The Taoiseach, Mr Ahern, is expected to be the only European Union prime minister at a United Nations special session on HIV/AIDS at UN headquarters in New York this week.
The UN General Assembly has never held a special session on a health issue before. Two dozen heads of state or government, mostly from Africa, will be among the 3,000 delegates.
Mr Ahern will attend the second day of the session tomorrow and is expected to announce extra funds for assistance to developing countries including a substantial sum for the fight against HIV/AIDS.
The Minister of State at the Department of Foreign Affairs, Ms Liz O'Donnell, who has responsibility for the development aid budget, is also attending the special session.
Difficulties have arisen, mainly between Western and Islamic countries, over two issues. The first is the wording of the declaration to be adopted by the General Assembly at the close of the session on Wednesday. The second concerns an invitation to a gay and lesbian rights group to participate in one of the roundtable discussions which are a prominent feature of the special session.
Protracted discussions have been taking place over the weekend to resolve the difficulties: a meeting which began on Saturday at 10 a.m. continued until 2.30 a.m. next morning and was resumed yesterday afternoon.
Several Muslim countries, as well as the Vatican, are understood to have difficulty accepting language in the draft declaration specifying that special assistance in the treatment and prevention of HIV/ AIDS must be given to "men who have sex with men, sex workers, injecting drug-users and their sexual partners" along with other groups such as prisoners, refugees and migrants. (Sex workers is a euphemism for prostitutes.)
"There are intensive efforts going on to find a form of words acceptable to everybody," according to Irish diplomatic sources. Sweden, which holds the European Presidency, is speaking on behalf of all 15 member-states, including Ireland, and there are regular co-ordination meetings of EU members to agree a joint position.
Sources said the EU was arguing that refusing even to name particularly vulnerable groups was compounding a sense of denial about HIV/AIDS which would only facilitate the spread of the disease. However, some Muslim countries consider recognition of homosexuality as a religious and cultural insult.
The second difficulty concerns the admissibility of the San Francisco-based International Gay and Lesbian Human Rights Group to a round-table discussion on "HIV/AIDS and Human Rights". The president of the General Assembly, Mr Harri Holkeri of Finland, a former co-chairman of the Northern Ireland peace talks, had originally included the group's representative, Ms Karen Kaplan, on the panel.
Several Muslim countries, believed to include Egypt, Libya and Pakistan, objected, and her name was removed from the list. In response, Canada tabled a General Assembly resolution to have the invitation restored. The motion has the support of the EU member-states, including Ireland, along with Australia, New Zealand, Chile, Iceland and others.
It will be a considerable political embarrassment if the two issues are not resolved quickly. Normally, draft declarations are agreed in advance so that visiting prime ministers and foreign ministers do not become embroiled in last-minute negotiations. Likewise, a wrangle over the Canadian motion at the General Assembly today would be considered damaging in public relations terms.