Major Western nations, including Australia, are protesting a move to block gay and transgender groups from attending a high-level United Nations conference on AIDS.
A UN diplomat said on Wednesday that the Organisation of Islamic Countries, made up of 51 nations, asked that 11 groups not be allowed to attend the conference next month.
Other countries also objected to a number of other groups, bringing the total number of excluded groups to 22.
The official spoke on condition of anonymity because the communications have been private.
In a letter to General Assembly President Mogens Lykketoft, US Ambassador Samantha Power said the groups that were singled out appeared to have been chosen for their involvement with gay and transgender issues and asked that all groups that have requested participation will be allowed to attend.
"Given that transgender people are 49 times more likely to be living with HIV than the general population, their exclusion from the High Level meeting will only impede global progress in combatting the HIV/AIDS pandemic and achieving the goal of an AIDS-free generation," the letter, dated May 13, stated.
The European Union letter, signed by Ambassador Joao Vale de Almeida, expressed concern that the groups had been struck from the initial list of participants at the conference and asked for information about which countries objected and why.
"If you're serious about getting to zero (AIDS cases), then it's vital to include all communities.
"It's wrong to block access to the UN for transgender organisations and gay organisations that have every right to participate in this important discussion," Britain's deputy UN ambassador Peter Wilson said.
Canada's Ambassador and Deputy Permanent Representative Michael Grant said his country also sent a letter expressing concern that members could remove civil society groups from a conference without providing any justification.
"It's quite concerning, especially on an issue like HIV/AIDS," Grant said. Australia has also written a letter of protest.
When Lykketoft negotiated arrangements late last year for the AIDS conference, to be held at UN headquarters on June 8-9, some members insisted on being able to object to an NGO's participation without any public explanation.
On Wednesday, Lykketoft responded to the protests in letters saying that he had done everything in his power to ensure the broadest participation but he was limited by his mandate which did not allow him to provide the names of the objectors.
While Secretary-General Ban Ki-moon has long been out front on issues involving lesbians, gays, bisexuals and transgender people, many of the member states have been less supportive.
Earlier this week, the world body allowed a gay rights group to host a gala at UN headquarters for the first time and last August the Security Council held its first meeting spotlighting violence and discrimination against LGBT people.
