Jean-Marie Guéhenno, the under-secretary-general for peacekeeping operations, said in New York that the peacekeepers represented "the best the international community has to offer".
Seventeen peacekeeping operations under way around the world.
Most current missions are in Africa - in countries such as Sudan, the Democratic Republic of Congo and the border areas of Ethiopia and Eritrea.
In Europe, UN peacekeepers are in Georgia and Kosovo. In Cyprus they aim to prevent further clashes between Greek and Turkish communities.
Observers are stationed across much of the Middle East, monitoring ceasefires and attempting to prevent escalating violence.
In Asia, there are missions in India, Pakistan and East Timor.
And the sole UN mission in the Americas is in Haiti, which has been in effect since 2004.
The greatest number of troops come from Pakistan with Bangladesh and India supplying the second and third highest number.
But UN peacekeepers, famous for their blue helmets, have come under increasing criticism in recent years for alleged misconduct.
On Wednesday, Save the Children issued a report that said children in the Ivory Coast, Sudan and Haiti had been abused by United Nations staff.
The UN Department for Peacekeeping Operations was said to be the body most likely to be responsible for abuse.
The reputation of UN peacekeepers has been tarnished in the past by cases of sexual abuse against women, notably in the Democratic Republic of Congo (DRC), Ivory Coast and Haiti.
In November last year, the UN said that more than 100 Sri Lankan soldiers were to be sent home over charges that they paid for sex while stationed in Haiti.
In 2005, the world body recommended that the soldiers involved be punished, their salaries frozen and a fund set up to help any women or girls who became pregnant.
The UN's "zero tolerance" policy towards sexual misconduct includes a "non-fraternisation" rule barring them from sex with locals.
As well as abuse allegations, the world body has faced wider criticism that peacekeepers have proved ineffective, failing to prevent genocide in Rwanda in 1994 and the massacre of 7,000 Bosnian Muslims by Bosnian Serbs in 1995.
The UN's first peacekeeping operation was to monitor a ceasefire between Arab and Israeli forces in 1948 - it is still ongoing.