Israeli officials say no decision has been made on military action against Iran's nuclear programme, despite reports that the window for a pre-emptive strike is closing.
A government source told Sky News "all options remain on the table" but refused to comment on growing media speculation that a strike would take place by the summer of 2012.
Israel's defence minister Ehud Barak has warned that "time is urgently running out" to prevent Iran from developing nuclear weapons.
He said the Iranians are "deliberately drifting into what we call an immunity zone where practically no surgical operation could stop them."
Mr Barak was referring to Iran's efforts to move critical elements of its nuclear programme - including uranium enrichment - deep underground.
Iran's main enrichment site at Fordo, near Qom, is beneath 90 metres of rock, perhaps beyond the reach of even the huge bunker-busting bombs Israel is known to possess in its arsenal.
Tehran claims it is developing nuclear technology for civilian purposes but the latest report from the UN's nuclear watchdog said Iran was carrying out work that could only be related to the future development of a nuclear weapon.
Unnamed Israeli defence officials quoted by the Associated Press said even a strike right now would probably only delay Iran's nuclear ambitions by two or three years rather than halt them altogether.
Another consideration is the reaction to such a strike.
Iran is likely to retaliate directly - firing missiles towards Israel - and through its regional allies.
The Iranian-sponsored Lebanese militia Hizbollah could fire a hail of rockets into Israel, Hamas could also step up rocket fire from Gaza.
The risk of regional conflagration is being weighed by Israel against the dangers of a nuclear Iran.
Publicly, the Israeli government still favours diplomacy and sanctions to bring Iran into line.
That could also be the position privately, with all of the sabre rattling part of the necessary pressure to bring the international community together to act.
There is also awareness that Israel will need a green light and military back-up from Washington and President Obama would probably prefer to wait until after the US election in November.
The bottom line, according to most analysts, is that Israel is never going to lay out a timetable for action.
It needs to keep the threat of it ever present but when - and if - a military strike comes, Tehran will not get notice first.