Iran has enough radioactive material to produce four nuclear bombs, Israel's chief of military intelligence, General Aviv Kochavi, asserted at a security conference on Thursday.
"Today international intelligence agencies are in agreement with Israel that Iran has close to 100 kilograms (220 pounds) of uranium enriched to 20 percent, which is enough to produce four bombs," he told the annual Herzliya conference.
"Iran is very actively pursuing its efforts to develop its nuclear capacities, and we have evidence that they are seeking nuclear weapons," he said.
"We estimate they would need a year from when the order is given to produce a weapon."
Israel and much of the international community have long accused Iran of using its nuclear programme to mask a drive for weapons, a charge Tehran denies.
The Jewish state has pushed for tough sanctions against Iran and warned that it retains the option of a military strike if necessary to prevent Tehran from obtaining atomic weapons.
Israel has the Middle East's sole if undeclared nuclear arsenal, which international experts believe contains between 100 and 300 nuclear warheads, but has never confirmed or denied such reports.
Speaking at the same conference, Strategic Affairs Minister Moshe Yaalon said Iranian nuclear facilities, believed to be underground and heavily reinforced, were not immune to attack.
"In my military experience, any site protected by humans can be penetrated by humans," said Yaalon, a former head of Israel's armed forces, in comments broadcast on Israeli public radio. "At the end of the day all their sites can be hit."
"We argue that one way or another the Iranian military nuclear programme must be stopped," he added. "Such an unconventional regime must not have an unconventional (weapons) capability.'
"A combination of tools are available to the West," Yaalon said. "That combination must include diplomatic isolation of the regime; the second tool is economic sanctions ... and the last thing is a credible military option."
Yaalon also referred to an Iranian military facility rocked by a deadly explosion in November, claiming Iran had been developing a missile there intended to threaten the United States.
He said the site, at Bid Ganeh, near Tehran, was conducting research and development on a missile with a range of 10,000 kilometres (6,213 miles) at the time of the blast, which killed at least 36 Revolutionary Guards.
It was "aimed at America, not us," a statement from the organisers of the Herzliya Conference quoted him as saying.
Iran's military said the explosion was the result of an accident.
The chief of staff of Iran's armed forces said at the time that the base was used in the production of "an experimental product" that would unleash "a strong fist in the face" of the United States and Israel.
Also on Thursday, Israeli Defense Minister Ehud Barak praised new European sanctions against Iran after talks with German Foreign Minister Guido Westerwelle, but sidestepped questions about possible military action.
"Military plans in general are not a matter for public discourse," Barak said. "Today we are still in a period of diplomacy and sanctions."
"It is obvious to everyone that no option should be removed from the table and that diplomacy must be conducted intensively and urgently. The sanctions on Iran must include not only the oil sector -- but also the financial system and the central bank."
Kochavi also warned Thursday that Israel's enemies now command "some 200,000 rockets and missiles."
Intelligence estimates, he said, showed "one in every 10 houses in south Lebanon is a storage facility for missiles or rockets or a launch pad for devices that are increasingly accurate and destructive."
"From Lebanon, Syria and of course from Iran, they can hit the heart of our cities, and the whole region of Tel Aviv is within their reach," he said.