Rouhani, a moderate cleric who won the presidential election in June, is to take the oath of office in Iran's parliament Sunday.

Rouhani, 64, a former key Iranian negotiator on nuclear issues, gained more than 50 percent of the votes in the country’s presidential elections on June 14. He will replace outgoing Ahmadinejad whose presidency has seen sharp deterioration in ties with Europe and the United States and the imposition of economic sanctions provoked by international opposition to Tehran's nuclear program.

Western countries suspect Iran of using its nuclear program to develop atomic weapons capability, a claim Iran has consistently denied. Tehran claims it needs atomic technology for producing electricity, although it has some of the world's largest reserves of oil and gas.