Washington (CNN) -- An International Atomic Energy Agency report to be released this week will say that Iran has mastered the critical steps necessary to design and construct a nuclear weapon, Western diplomats briefed on the report told CNN Monday.
The report says there is no evidence Iran has made a strategic decision to actually build one, the diplomats said.
The report will contain the most detailed charges to date that Iran's nuclear program is geared toward weapons development and military use, the diplomats said. It will include more data than the organization has previously released on alleged clandestine efforts by Iran to develop technologies to build a nuclear weapon, including computer models of a nuclear warhead. They argue the IAEA studies offer no other explanation for those efforts beyond Iran seeking to develop a nuclear weapon.
Iran has repeatedly insisted its nuclear program is for peaceful, civilian energy purposes only.
Iran's state-run media, Monday carried quotes from a top cleric Monday warning the IAEA not to "defame" itself "by unveiling false documents."
IRNA reported that Tehran's Eid-al-Adha Prayer Leader, Ayatollah Ahmad Khatami, was warning IAEA Director General Yukiya Amano "against disclosure of forged documents against Iran."
The Western diplomats, who spoke on condition of anonymity before the report is released, said the report will say Iran's weapons program is more ambitious and structured, and more progress has been made, than previously known -- and that the program is aimed at building and testing a nuclear weapon that can be fitted and delivered on a long-range missile.
According to the report, Iran is believed to have continued weapons research and technology development after 2003, when the intelligence community thought Iran had stopped, the diplomats said. Instead of halting, it seems Iran took a temporary hiatus at the time, although the program progressed at a more modest pace since then, the diplomats said.
Previous IAEA reports have cited concerns by the organization that Iran has been seeking to develop nuclear warheads and ballistic missiles to deliver them.
The United States and other Western powers suspect Iran's nuclear program is geared toward weapons development.
The United States is looking to increase the heat on Iran, including a possible strengthening of existing sanctions on Iran's financial and banking sectors and additional political pressure -- all of which could be applied by the United States alone or in coordination with other allies. The United States also hopes international organizations, such as the United Nations, will take steps to further isolate Iran diplomatically.
Officials said that one of several options being considered is sanctioning the Central Bank of Iran, although the United States is mindful of the impact such a move could have on oil prices during a time of global economic turmoil.
U.S. officials said the administration of President Barack Obama will use the report to lobby the international community to slap new economic sanctions against Iran. Obama said he discussed the upcoming report with French President Nicolas Sarkozy in Cannes, France, during a meeting of the G-20 industrialized nations. The U.S. president said the two leaders "agreed on the need to maintain the unprecedented international pressure on Iran to meet its obligations."
White House spokesman Jay Carney said Monday that while he did not "want to get ahead of the report, I do expect it will echo our concerns. And I think that the fact that Iran continues to misbehave, if you will, is something that concerns not just the United States, but the broader international community. And that international community, because of the actions we have taken, is now focused on pressuring Iran. ... You can be sure that we will continue to work to pressure Iran, to isolate Iran."
The IAEA report comes on the heels of recent U.S. allegations of an Iranian plot to assassinate the Saudi ambassador to Washington and could strengthen the U.S. case for tougher measures against Iran.
The Obama administration has publicly downplayed speculation that the United States and Britain are weighing a military strike against Iranian nuclear facilities, saying U.S. officials are focused on a diplomatic strategy.
However, some officials say privately the U.S. military and intelligence community is growing increasingly concerned that Israel could be preparing a strike and are monitoring both Israel and Iran closely.
Russia on Monday warned Israel not to take such action. "Our position towards this issue is well known. We think it would be a very grave mistake fraught with unpredictable consequences," Russia's Foreign Minister Sergey Lavrov said Monday on state-run Russia 24 television.
"There is no military solution to the Iranian nuclear problem, or to any other international issues for that matter. We get evidence of that every day when we're looking at developments around Iraq, Afghanistan and other countries of that region. Military interference only increases the number of victims and human suffering," he said.
Lavrov added, "The use of force is possible only in two cases under the U.N. Charter: when the right of self-defense is exercised, and when there is a corresponding resolution of the U.N. Security Council. I hope such cases will not emerge."
CNN's Alla Eschenko and Josh Levs contributed to this report.