Iran has given $500 million in official assistance to Afghanistan for infrastructure and other reconstruction projects in recent years, Mahmoud Barimani, a senior Iranian Foreign Ministry official, told the United Nations General Assembly on Thursday. Mr. Barimani accused the United States and its allies of destabilizing Iran’s neighbor and increasing the violence there rather than solving the country’s problems. In 2006, Iran reported that its aid had totaled $200 million. Last month President Hamid Karzai of Afghanistan admitted that Iran had given his office “bags of money” worth millions of dollars. Mr. Barimani did not mention those payments.