The Council for Global Equality wants the American government to defend the rights of lesbian, gay, bisexual and trans people across the world.
"The Project demands that those who represent our country - in Congress, in the White House, in US embassies and in US corporations around the world - use the diplomatic, political and economic leverage available to them to oppose human rights abuses that are regularly directed against individuals because of their sexual orientation, gender identity or gender expression," the group states on its website.
Ambassador Michael E Guest retired from government service last December after more than 26 years as a form of protest against regulations that he considered as unfair to same-sex partners.
The 51-year-old, who is openly gay, served as US Ambassador to Romania when President Bush took office.
He will work as a paid consultant to the group, which will hold its first meeting in Washington DC on September 23rd.
Mr Guest was the first out gay person to be confirmed by the Senate to an ambassadorial post.
In May the British government adopted an official programme to support the human rights of gay, lesbian, bisexual and trans people in other countries.
The Foreign and Commonwealth Office issued an 'LGBT Toolkit' to its 261 embassies, high commissions and other diplomatic posts.
"The FCO fully supports equality in the enjoyment of human rights and the inadmissibility of discrimination on grounds of sexual orientation," the document states.
"This provides the focus of FCO work on this issue."
The kit contains information on the official British policy on gay rights and instructions in how to "provide added value to equality and non-discrimination work."
"Governments have an obligation to promote equality in the enjoyment of human rights, as well as not to discriminate in their application.
"Frequently there is discrimination in the enjoyment of key rights, even in countries where the criminal laws are neutral.
"Tackling this would require the building up of local coalitions of non-state actors to elaborate action plans for each country, as well as working locally with like-minded states.
"This would not just apply to issues like the state of the criminal law, but also to freedom of association and assembly, freedom of expression and privacy."
The 'toolkit' covers a wide range of issues, from decriminalisation, sexual health, reproductive rights and health education to bilateral work with other countries.
The UK and France both support the universal decriminalisation of homosexuality.
France, as President of the EU, has said it will present a declaration on the matter to the UN Security Council in December.