VIENNA — Despite some remaining differences, a deal has been reached with Iran that will allow the U.N. nuclear agency to restart a long-stalled probe into suspicions that Tehran has secretly worked on developing nuclear arms, the U.N. nuclear chief said Tuesday.

The news from International Atomic Energy Agency chief Yukiya Amano, who returned from Tehran on Tuesday, comes just a day before Iran and six world powers meet in Baghdad for negotiations and could present a significant turning point in the heated dispute over Iran’s nuclear intentions. The six nations hope the talks will result in an agreement by the Islamic Republic to stop enriching uranium to a higher level that could be turned quickly into the fissile core of nuclear arms.

There was a possibility that the conference may be delayed by weather. A sand storm closed Baghdad’s airport’s Tuesday.

Iran insists its nuclear program is only for electrical power and medical applications, not weapons.

On Tuesday, the official Islamic Republic News Agency reported that Iranian scientists had inserted a domestically made fuel rod, which contains pellets of 20 percent enriched uranium, into the core of a research nuclear reactor in Tehran.

The advance would be another step in achieving proficiency in the entire nuclear fuel cycle. Iran said in January that it had produced its first nuclear fuel rod, and that it had to make them because Western sanctions prohibit their purchase abroad.

By compromising on the IAEA probe, Iranian negotiators could argue that the onus was now on the other side to show some flexibility and temper its demands. Although Amano’s trip and the talks in Baghdad are separate, Iran hopes progress with the IAEA can boost its chances today in pressing the U.S. and Europe to roll back sanctions that have hit Iran’s critical oil exports and blacklisted the country from international banking networks.