NATO said in June the Afghan military was in charge of national security operations in the country. International forces operating in Afghanistan are transitioning from a combat to an advisory role as they make preparations to leave the country next year.
U.N. Deputy Secretary-General Jan Eliasson said the world body would stay committed to Afghanistan as it undergoes transition.
"Afghanistan continues to be a major priority for the United Nations, and we believe that we will be able to see progress and success by working together closely," he said in a Tuesday statement.
The British government's monthly assessment of Afghan troop strength indicated challenges would endure during the summer months because of the heavy fighting associated with the melting of seasonal snows.
British Prime Minister David Cameron visited his troops last weekend in Afghanistan. He said he was confident about the ability of Afghan national forces, but said "a strong security response, must also be accompanied by a strong political response."
Afghanistan holds elections next year.