U.N. Secretary-General Kofi Annan said after meeting Iranian Foreign Minister Manouchehr Mottaki on Thursday that he believes Tehran is taking "very seriously" an offer of incentives to roll back its disputed nuclear program.

"I hope it will give its official answer before too long," Annan said, adding that it might come after the Group of Eight summit conference starting June 29 in Moscow.

But Iran's president said Wednesday his country would take until mid-August to respond to the incentives package, prompting President Bush to accuse Tehran of dragging its feet.

CountryWatch: Iran

The United States wants a fast response to the offer it made with the four other permanent members of the Security Council and Germany. The partners are holding open the option of seeking a U.N. Security Council resolution against Iran if they find its response unacceptable.

Annan said his talks with Mottaki were "very useful."

"Iran maintains that its interest in nuclear energy is purely for peaceful purposes, and I have stressed to Iranian leaders, including Mr. Mottaki, that it is very much in their interest to convince the world of that by cooperating fully with the IAEA (International Atomic Energy Agency)," Annan told reporters.