Mark it down in your calendars - spring 2010. If everything taking place right now on the Iranian front continues as expected, it is then that Israel will need to make one of its most difficult decisions ever - to attack Iran or allow it to continue with its nuclear program. By the spring of 2010, Israel will know the results of the dialogue between the world's leading powers and Iran that is scheduled to begin on October 1, as well as whether the world will impose real, tough sanctions. Following the disclosure last week of the existence of a secret uranium enrichment facility in a mountain near the holy city of Qom, there is a feeling in Israel that the world is now more serious than in the past regarding the need to talk tough with Iran and, if needed, to impose tough sanctions as well. This could be seen at the press conference in Pittsburgh on the sidelines of the G-20 meeting, during which Barack Obama, Nicolas Sarkozy and Gordon Brown all spoke tough to Iran. The testing of long-range missiles by Iran on Monday, Yom Kippur, was on the one hand a flexing of Iran's muscles in face of this possibility, but was also a move that will definitely put more world attention on its nuclear program. The discovery of the second enrichment facility - not large enough to be used for energy purposes like the known facility, Natanz - validates one of Israel's gravest concerns in recent years, that Iran was building a bomb using hidden facilities. Iran could continue to enrich uranium to low levels, below 5 percent, at Natanz - which is under IAEA supervision - and enrich uranium to higher, military levels at the underground facility near Qom without anyone knowing. As US Secretary of Defense Robert Gates - one of the fiercest opponents under the Bush administration of military action against Iran - said on Sunday, there was no longer any real doubt that Iran was seeking to develop nuclear weapons. It is under these assumptions that the Americans will enter the dialogue with Iran, slated to begin on Thursday. While Israel is extremely skeptical of a positive outcome from the talks, there is an understanding that it will need to wait for the dialogue to finish before taking any unilateral action. This leaves three likely scenarios. The first is that the dialogue fails and the EU, Russia, US and China decide to impose tough sanctions on Iran, particularly in the energy sector and supply of refined fuel, a measure believed to be capable of having a real effect on the regime. Israel would then have to give the sanctions time, to wait to see if they are effective. The second scenario is that the US and Iran reach a deal under which the Islamic republic is allowed to continue enriching uranium at low levels for energy purposes but would have to agree to new supervision measures and to keep all of its international obligations. If this happens, the Obama administration will likely laud the deal as a major diplomatic success - particularly in the absence of one with North Korea - and would effectively tie Israel's hands. The third scenario is that the talks will fail, the world powers will not agree to impose sanctions and Israel will be left to decide whether or not it will strike Iran. This would likely happen sometime around spring 2010. The success of such a strike has been under question for several years now. In an article in The Wall Street Journal over the weekend, Anthony Cordesman, a respected American national security analyst, wrote, "It is far from certain that such action would be met with success." Nevertheless, Cordesman conceded that Israel was very serious regarding the military option and would likely focus any strike on three targets - the Busher reactor, Natanz and the Arak heavy water facility. The enrichment center near Qom, as well as known Iranian airfields, missile silos and launchers can also be added to the list. While Natanz is heavily fortified and built in an underground bunker, Cordesman said that Israel would be able to use some of the GBU-28 bunker buster missiles it purchased from the US to penetrate the facility. He also raised the possibility that Israeli intelligence had gotten its hands on US, European and Russian designs for more advanced weapons than the GBU-28. The assessment in the defense establishment is that the fallout from such a strike would be three times that of the Second Lebanon War, the First Gulf War and the attacks on the Israeli Embassy and Jewish center in Argentina in the 1990s combined. At the moment all eyes are on this Thursday, when the dialogue begins, but as recent events have shown, time is running out.