Mahmoud Ahmadinejad is being urged to do more to help resolve the row over Iran’s nuclear programme.
The appeal comes from the UN Secretary General Ban Ki-moon in a meeting with the Iranian president in New York.
Ahmadinejad is due to address the General Assembly this week.
In a TV interview he said the US had to accept that Iran is a major world power, repeating denials that it wants to create nuclear bombs. He has also called on Washington to release eight Iranian prisoners as what he calls a “humanitarian gesture.”
Last week, Iran released one of three American hikers detained since last summer.
Protests against Ahmadinejad’s visit are expected throughout the week in New York.
Ban Ki-moon has called on Iran to “engage in a constructive manner” in nuclear talks. He says he also stressed the importance of respecting fundamental rights.