The United Nations' top nuclear official will travel to Tehran on Sunday for talks with senior Iranian officials as speculation mounts about a possible breakthrough on Iran's controversial nuclear program.

The Vienna-based International Atomic Energy Agency announced the surprise visit Friday. An IAEA statement said Director General Yukiya Amano would travel to Iran to “to discuss issues of mutual interest with high Iranian officials.”

Western diplomats said this week that the IAEA and Tehran have been making progress on a possible deal that would allow the nuclear watchdog to resume its investigation into allegations Iran is trying to develop nuclear weapons.

The talks in Tehran are set to take place just two days before a separate meeting between Iran and world powers in Baghdad.

The P5+ 5 group, which includes the five permanent member of the United Nations Security Council and Germany, has been trying to assess the possible military capability of Iran's nuclear sites.

The West and Israel fear Iran is developing nuclear weapons under the cover of an energy program. Iran says its nuclear ambitions are peaceful.

Iran has barred the U.N. nuclear agency from the Parchin military site near Tehran.

Western officials suspect Iran has built a container there that could house nuclear explosives tests and accuse Tehran of trying to remove incriminating evidence before allowing U.N. inspectors inside the facility. Iran has dismissed the allegations as being “childish” and “ridiculous.”

During a visit to Prague Friday, Israeli Prime Minister Benjamin Netanyahu warned Tehran might be trying to buy time in order to further advance its weapons ambitions.

Iran has long denied the Israeli and Western accusations.

But Mr. Netanyahu said Friday that “Iran is very good in playing this kind of chess game.”

Both Israel and the United States have refused to rule out using military force as a last resort in order to prevent Iran from developing nuclear weapons.