UN Secretary-General Antonio Guterres has arrived in the Central African Republic amid mounting communal violence and a deteriorating humanitarian situation.
The UN chief has called the country one of the world's most dangerous places for aid workers to serve.
Already a dozen UN peacekeepers have been killed.
Mr Guterres has recommended that the number of peacekeepers be increased by 900 to a total of about 12,000.
The United States has been seeking to cut the costs of UN peacekeeping operations but Mr Guterres has said more are needed in Central African Republic to protect civilians.
Mr Guterres is also accompanied on his trip by the United Nations' first victims' rights advocate, Jane Connors.
Central African Republic is where the largest number of sexual abuses allegations was made against peacekeepers last year.