Iran appears to have worked on designing an atomic bomb 0911111.

The report immediately exposed splits among the big powers about how best to handle the row over Iran's nuclear aims: the United States signaled tougher sanctions on Tehran but Russia said the report could hurt chances for diplomacy.

It was preceded by Israeli media speculation that the Jewish state may strike against its arch foe's nuclear sites. But Defense Minister Ehud Barak said on Tuesday no decision had been made on embarking on a military operation.

Iran, which denies it wants nuclear weapons, condemned the findings of the Vienna-based International Atomic Energy Agency (IAEA) as "unbalanced" and "politically motivated."

Russia and the United States are among the six big powers -- also including China, Britain, France and Germany -- which have been involved in stalled attempts to find a diplomatic solution to the nuclear dispute with Iran.

Tehran has for years dismissed allegations of atomic bomb research, based largely on Western intelligence funneled to the IAEA, as fabricated and baseless, and more recently sought to discredit Amano as a tool of Washington.

The IAEA said it had carefully assessed intelligence passed on from member states and found it consistent in terms of technical content, individuals and organizations cited and time frames. It said it had gathered its own supportive details.

The IAEA "has serious concerns regarding possible military dimensions to Iran's nuclear program," the U.N body said in the report, which included an unusual 13-page annex with technical descriptions of research with explosives and computer simulations applicable to nuclear detonations.

U.S. spy services estimated in 2007 that Iran had halted outright "weaponisation" research four years previously, but also that the Islamic Republic was continuing efforts to master technology usable in nuclear explosives.

The IAEA report included information from both before and after 2003. It voiced "particular concern" about information given by two member states that Iran had carried out computer modeling studies relevant to nuclear weapons in 2008-09.

The information also indicated that Iran had built a large explosives vessel at the Parchin military complex southeast of Tehran in which to conduct hydrodynamic experiments, which are "strong indicators of possible weapon development."