"It is important for the dialogue with Iran to be limited in time," Lieberman's office quoted him as telling Italian Prime Minister Silvio Berlusconi in Rome.

"If after three months it becomes clear that the Iranians are buying time and not halting their nuclear programme, the international community will have to take practical steps against them," he added.

Six world powers led by Washington last month decided to invite Iran for direct talks on its nuclear programme amid Western suspicions it is cover for a drive for an atomic bomb, something Tehran strongly denies.

Widely considered to be the Middle East's sole nuclear armed power, Israel considers Iran its arch-enemy because of repeated statements by President Mahmoud Ahmadinejad that the Jewish state is doomed to be wiped off the map.

Israel's new Prime Minister Benjamin Netanyahu has said repeatedly that Iran's nuclear programme constitutes the biggest concern for the Jewish state since its creation in 1948.

US President Barack Obama has struck a softer tone towards Iran in a break with the hard line taken by his predecessor George W. Bush.

But Secretary of State Hillary Clinton said last Wednesday that the new administration would be prepared to push for tough new sanctions against Iran if dialogue fails.