GENEVA, July 11 -- Failure to provide adequate HIV services for certain key populations threatens global progress on the HIV response, the World Health Organization (WHO) warned on Friday.

According to a new HIV guideline released by the WHO, these populations include men who have sex with men, people in prison, people who inject drugs, sex workers and transgender people.

"Failure to provide services to the people who are at greatest risk of HIV jeopardizes further progress against the global epidemic and threatens the health and wellbeing of individuals, their families and the broader community," Gottfried Hirnschall, director of the HIV department at the WHO, said in a statement.

The guideline outlines steps for countries to reduce new HIV infections and increase access to HIV testing, treatment and care for these five key populations.

For the first time, the WHO strongly recommended men who have sex with men consider taking antiretroviral medicines as an additional method of preventing HIV infection alongside the use of condoms.

The WHO estimated that globally 20-25 percent reductions in HIV incidence among men who have sex with men could be achieved through pre-exposure prophylaxis, averting up to 1 million new infections among this group over ten years.

In the guideline, WHO also recommended that countries address the legal and social barriers that prevent many from seeking medical services.