Israeli Defence Minister Ehud Barak said on Monday that Iran's recently diclosed second uranium enrichment plant is "immune" to conventional bombing.

"The new site near Qom is meant for enrichment. What was revealed by the Iranians had been built over years and is located in bunkers that cannot be destroyed through a conventional attack," Barak told parliament's foreign affairs and defence committee.

Iran notified the UN nuclear watchdog in September that it was building a second enrichment plant near the central shrine city of Qom, after Washington accused it of covertly evading its notification responsibilities under the Non-Proliferation Treaty.

Confirmation of the construction work drew criticism not only from Western governments but also from the United Nations.

Enriched uranium can make the fuel for nuclear power plants but in highly extended form can also produce the fissile core of an atomic bomb.

Along with Western governments, Israel suspects Iran of seeking to develop a weapons capability under the guise of a civil nuclear programme, an accusation Tehran denies.

Along with its US ally, Israel, the region's sole if undeclared nuclear power, has refused to rule out a resort to military action to prevent Iran developing a bomb.

Barak said he feared Iran could develop a weapon by 2011.

"I believe that by early 2010 Iran will hold threshold technology (for building a bomb). That means that if it wanted, it could develop nuclear weapons within a year from obtaining threshold technology," a senior official quoted him as telling the parliamentary committee.