Iran's nuclear program is the focus of two separate meetings Wednesday, but no major breakthroughs are expected ahead of the country's June presidential election.
The U.N. nuclear agency is holding a 10th round of talks since the beginning of last year with Iranian officials, as its investigators continue to seek access to Iran's nuclear facilities and documents.
The International Atomic Energy Agency is concerned about Iran's potential development of nuclear weapons, and wants to visit facilities such as the Parchin military site to resolve questions about the program.
Iran insists Parchin is a standard military facility and that its nuclear program has only peaceful purposes.
Meanwhile, in Istanbul, Iran's top nuclear negotiator Saeed Jalili will hold talks with European Union policy chief Catherine Ashton.