Iran has enough low-enriched uranium to make two weapons, which it could have prepared and ready for delivery as early as 2012, CIA director Leon Panetta said Sunday.

"We think they have enough low-enriched uranium for two weapons," Panetta told the ABC network's "This Week" program.

Tehran would need a year to enrich it fully to produce a bomb and it would take "another year to develop the kind of weapon delivery system in order to make that viable," he said.

Iran is under mounting international pressure over its suspect nuclear program, which the West fears masks a covert weapons drive.

The Islamic republic vehemently denies the charge, but has been flexing its military muscle mainly in the strategic Gulf region by staging regular war games and showcasing an array of Iran-made missiles.

"There is a continuing debate right now about whether or not they ought to proceed with a bomb. But they clearly are developing their nuclear capability and that raises concerns," Panetta said. "Just exactly what are their intentions?"

Neither the United States nor its top regional ally Israel, the sole if undeclared nuclear-armed power in the Middle East, have ruled out a military strike to curb Iran's atomic drive.

"Israel is very concerned about what's happening in Iran," Panetta noted.

"We continue to share intelligence (with Israel) as to what exactly is Iran's capacity," Panetta told ABC, but added that Israel is "willing to give us the room to be able to try to change Iran diplomatically and culturally and politically."

Israel, he said, feels "more strongly that Iran has already made the decision to proceed with the bomb, but at the same time they know that sanctions will have an impact."

Reacting to Panetta's warning about Iran being close to building an atomic bomb, Russian President Dmitry Medvedev said there was cause for concern.

"This information has to be checked but such information is always worrying and all the more so because the international community does not recognize the Iranian nuclear program as transparent," he told reporters at the G20 summit in Toronto.

"If this is proved, it would make the situation even more tense," Medvedev said, adding that Russia might need to re-examine its position on the matter.

Russia, which unlike the United States has diplomatic ties with Iran, has in the past been reluctant to impose tough sanctions but backed the latest UN move following Tehran's repeated defiance of orders to halt uranium enrichment.

The US Congress this week endorsed a sweeping package of tough new energy and financial sanctions on Tehran over the program, and on June 10 the UN Security Council adopted resolution 1929, which imposes military and financial sanctions on Iran aiming to rein in the suspect nuclear drive.

The new US measures being sent to President Barack Obama for his signature, piled atop the UN Security Council and European sanctions, are aimed to choke off Iran's access to imports of refined petroleum products like gasoline and jet fuel and curb its access to the international banking system.

The bill would also shut US markets to firms that provide Iran with refined petroleum products that the oil-rich nation must import to meet demand because of a weak domestic refining capability, and takes aim at firms that invest in Iran's energy sector, including non-US companies that provide financing, insurance, or shipping services.

Iranian President Mahmoud Ahmadinejad has lashed out at the international community in the wake of sanctions, charging that the UN Security Council has become an "oppressive tool" of world powers.

In an outburst earlier this month against the Security Council for imposing the new round of sanctions, the hardline president said the UN body had failed to resolve any key world issues, including conflicts in Iraq and Afghanistan.

"We continue to urge them to engage in peaceful use of nuclear power," Panetta said Sunday.

"If they did that, they wouldn't have these concerns, they wouldn't have these problems. The international community would be working with them instead of having them work on their own."

At a G8 meet in Canada meanwhile world leaders urged Iran to hold a "transparent dialogue" over its nuclear program, as Ahmadinejad prepared to unveil his conditions for talks.