Prime Minister Benjamin Netanyahu said on Monday that Israel had benefited from what he called the Iranian government's loss of legitimacy, both among other states and with its own people.

Speaking to a closed session of the parliamentary defense committee, as quoted by an official, Netanyahu repeated his view that Israel must prevent Iran acquiring nuclear weapons but gave no indication of if or when Israel might use military force -- an option his government has refused to rule out.

However, on a day of clashes between protesters and police in Tehran, and a week after Iran defied international pressure and announced an expansion of a nuclear program it says is for purely civil use, Netanyahu told Israeli lawmakers that the Iranian government was losing support at home and abroad.

"During the past year, Iran has lost a lot of legitimacy in the international community. This is an important asset to Israel," Netanyahu was quoted as saying by a parliamentary official. "Much of the Iranian population has animosity towards the regime."

The United States and its allies suspect Iran of pursuing nuclear weapons under cover of a civilian atomic energy program. Tehran denies this.

Many analysts take seriously the possibility that Israel, assumed to be the only nuclear military power in the Middle East, might at some stage consider launching a unilateral strike to prevent Iran acquiring a bomb, a prospect the Jewish state sees as an existential threat.

"SUPREME INTEREST"

Netanyahu said on Monday it was in Israel's "supreme interest to prevent Iran from arming with nuclear weapons".

But his government also appears keen not to break step with key ally the United States and other world powers, which are seeking to persuade Tehran to curb the military potential of its nuclear program by means of diplomacy and economic sanctions.

Should such diplomatic pressure weaken Iranian leaders, analysts say, that could reduce the chance of attacks on Iran.

Political sources have indicated Israel's armed forces have prepared plans for a possible strike on Iran, but analysts believe Netanyahu is content for now to follow the U.S. policy.

Earlier on Monday, an Israeli military intelligence officer also briefed the parliamentary defense committee on Iran.

Brigadier General Yossi Baidatz was quoted by a parliamentary official as saying that Iran had the nuclear know-how and the material, as well as the long-range missile technology, to build nuclear missiles to threaten Israel.

Echoing opinions expressed by Western experts, Baidatz said: "They have passed the technological stage. What now separates them from a (nuclear) bomb is taking the decision to build one."

On Monday, Netanyahu also reiterated Israel was prepared to hold peace talks with Syria, an ally of Iran on Israel's border, on condition Damascus did not insist the Jewish state concede beforehand that it would withdraw from all the Golan Heights, a strategic plateau Israel captured in a 1967 war.

Syria has signalled it would prefer to hold indirect talks, including the possible resumption of talks mediated by Turkey a year ago. Netanyahu said he preferred a French offer to mediate to that from Turkey, citing Istanbul's criticism of Israel's treatment of Palestinians, notably in last winter's war in Gaza.

Meanwhile, Iranian security forces have banned reformist students from leaving Tehran University to join protests at other universities, a reformist website said.

"Students of Tehran University are being prevented by security forces from leaving the university ... They wanted to join demonstrators at other universities," said the website which is run by reformist students.

Authorities also shut down both the mobile phone network in central Tehran to block supporters of Mirhossein Mousavi communicating with each other, according to the Web site said.

Thousands of Iranian riot police and Revolutionary Guard members armed with tear gas, batons and firearms were deployed Monday outside Tehran University to prevent student demonstrations backed by the opposition.

Two demonstrators were arrested during the clashes, said witnesses.

"Police are using batons to disperse demonstrators. People are chanting anti-government slogans in the Ferdowsi square," said the witness present at the state-organized rally, which protesters were expected to hijack for their own rally.

"There are hundreds of riot police, [they are] everywhere around Tehran University and nearby streets," said the witness, who asked not to be named.

The large security operation suggested that authorities planned to make good on their promise to deal harshly with protesters marking the day in 1953 when three students were killed in an anti-U.S. protest. The occasion has in recent years been used by students to stage pro-reform demonstrations.

Prime Minister Benjamin Netanyahu on Monday urged the West to use the social "power of the Internet" to counter the Iranian threat and the Islamic regime's crackdown on its own opposition.

Prime Minister Benjamin Netanyahu on Monday reiterated Israel's concern over Iran's contentious nuclear program.

"Iran is silencing all sources of information," said Netanyahu. "Using the power of the Internet and of Twitter against the Iranian regime is a tremendous thing that the United States can do."

The prime minister added that the "deep hatred among part of the Iranian nation against the regime" could serve as a "very important asset to Israel."

There was no word immediately available on whether the demonstrations in Iran have begun inside the campus, but the witnesses said police were conducting ID checks on anyone entering the campus to prevent opposition activists from joining the students.

Security forces also sought to conceal the campus from public view, covering the main gate and the fence with banners carrying quotations by Supreme Leader Ayatollah Ali Khameini and congratulatory messages marking an important Shiite occasion celebrated Sunday.

The deployment of security forces outside Tehran University led most stores and businesses in the area to shutter down. Life in the rest of the city, however, appeared to continue normally.

Journalists working for foreign media organizations are banned from covering Monday's planned protests. They were told late Saturday by the Culture Ministry that their press cards would be suspended for three days starting Monday.

On Sunday night, government opponents braved pouring rain to climb to Tehran rooftops and shout "Allahu Akbar" and "Death to the Dictator". Also Sunday, authorities choked off Internet access to deny the opposition a vital means of communication used in the past to mobilize supporters.

Government opponents were hoping for a large turnout for Monday's demonstrations to show their movement still has momentum despite a series of government crackdowns since the country's disputed presidential election in June.

Opposition leader Mir Hossein Mousavi threw his support behind the planned student demonstrations and declared that his movement was is still alive. A statement posted on his Web site said the clerical establishment cannot silence students and was losing legitimacy in the Iranian people's minds.

"A great nation would not stay silent when some confiscate its vote," said Mousavi, who claims President Mahmoud Ahmadinejad stole the June 12 election victory from him by fraud.

Khameini, the supreme leader who has finalsay on all state matters, accused the opposition Sunday of exposing divisions in the country and creating opportunities for Iran's enemies.

Iran's universities have been strongholds of the opposition movement that grew out of the disputed June election, and authorities have besieged campuses nationwide with a wave of arrests and student expulsions.

The pro-government Basij militia has also recruited informers on campuses to blow the whistle on any opposition troublemakers, according to students.

Despite heavy rain Sunday night, rooftop cries of Allahu Akbar or God is Great and Death to the Dictator were heard from many parts of Tehran on Sunday night. The protest reprised one of the main tactics of the anti-shah movement in the 1979 Islamic Revolution and was revived in the days and weeks after the disputed elections.

The rooftop chants had not been heard since the opposition's last attempt to mobilize, a Nov. 4 rally coinciding with state-sanctioned events to mark the anniversary of the 1979 U.S. Embassy takeover. That demonstration drew far fewer protesters than at the height of the summer's unrest. But it still provoked a violent response from security forces.

For weeks after the disputed June presidential election, demonstrations triggered by claims of massive fraud in the vote brought hundreds of thousands to the streets, but the relentless crackdown that followed has taken a heavy toll.

Seeking to deny the protesters a chance to reassert their voice, authorities slowed Internet connections to a crawl in the capital. For some periods on Sunday, Web access was completely shut down - a tactic that was also used before last month's demonstration.

The government has not publicly acknowledged it is behind the outages, but Iran's Internet service providers say the problem is not on their end and is not a technical glitch.

Seeking to confine journalists working for international media to their offices during the protests, Iran's Culture Ministry suspended accreditation allowing them to report from the streets from Monday to Wednesday.

The ministry also warned the few remaining pro-reform newspapers not to publish divisive material, the official IRNA news agency reported.

Largely swept off the streets, the opposition relies on the Web and cell phone service to organize rallies and get its message out.

The call for Monday's demonstrations was put out on dozens of Web sites run by supporters of opposition leaders Mousavi and Mahdi Karroubi, who both ran against Ahmadinejad in the June 12 election. Most of those sites have been repeatedly blocked by the government, forcing activists to set up new ones.