The activation of the Bushehr nuclear reactor in Iran demonstrates the international community's failure to stop the Islamic republic and the possibility that it will obtain a nuclear weapon, senior defense officials said Wednesday. "If they were not stopped until now, it is very possible that Iran will succeed in becoming a nuclear country," one senior defense official told The Jerusalem Post. "Israel, though, is not the only country that needs to be concerned. Iran is also a threat to Saudi Arabia, Bahrain and other countries in the Gulf," the official added. Defense Minister Ehud Barak said Wednesday that the test run at Bushehr and Iran's claims that it had increased the number of centrifuges enriching uranium to 6,000 constituted an existential threat to Israel. "Israel's policy is clear: We are not ruling out any option regarding the Iranian nuclear [program] and we recommend that others don't rule out any option either," Barak said in an address at the Interdisciplinary Center, Herzliya, in a hint to US President Barack Obama's administration. "A dialogue with Iran should be defined and limited in time." "Time is running out. Clear and decisive sanctions against the Iranian regime, alongside readiness to consider necessary actions in case the sanctions don't work, are necessary," Barak said. He added that Russia has had a crucial role in pressuring Iran, and that sanctions without Russia's participation would be meaningless. The power plant in the southern port city of Bushehr, built with Russian help, is meant to be the first in a number of reactors for an energy program. But the opening of the 1,000-megawatt light water reactor has long been delayed by construction and supply glitches. The United States for a time tried to dissuade Russia from helping the project. It's unclear when the reactor could be switched on. The tests, which began 10 days ago, "could take between four and seven months," Iran's nuclear chief, Vice President Gholam Reza Aghazadeh, told reporters at Bushehr. It was not known how long after the tests the reactor could start up. The plant, which will run on enriched uranium imported from Russia, has worried the West because the spent fuel could be turned into plutonium, a potential material for nuclear warheads. US concerns over the reactor softened after Iran agreed to return spent fuel to Russia to ensure Teheran does not reprocess it into plutonium. Washington largely dropped its opposition to the project and argued instead that the Russia fuel deal showed that Iran did not need its own domestic uranium enrichment program. Russia's fuel deliveries to Iran began in 2007. Enrichment is a concern because while low-enriched uranium is used as fuel for a reactor, higher-enriched uranium can be used to build a bomb. In the enrichment process, uranium gas is pumped through a series of centrifuges and spun at supersonic speeds to remove impurities. Aghazadeh announced that 6,000 centrifuges were now operating at Iran's enrichment facility in Natanz. He said Iran hoped to install more than 50,000 centrifuges there over the next five years. "We are doing what we need to do in Natanz on the basis of a specific time schedule," he told a press conference. Iran says it intends to use the enriched uranium fuel in its first domestically-built nuclear power plant in Darkhovin, which it wants to start operating in 2016. Aghazadeh said any delay in enrichment would mean a delay in opening Darkhovin. The tests at Bushehr consist of a computer run of the equipment to ensure there are no malfunctions when enriched uranium fuel is introduced into the reactor. No electricity will be produced during the tests. In the first stage of the test, technicians have for the past 10 days been loading "virtual fuel" into the reactor. The virtual fuel consists of lead, which imitates the density of enriched uranium, Iranian nuclear spokesman Mohsen Shirazi said. Once the fuel is fully loaded, "we will check to see how the reactor will operate," said Russian nuclear agency chief Sergei Kiriyenko, who was inspecting the process. "This [test] is one of the major elements of an extensive project," he said. Kiriyenko said Bushehr witnessed "remarkable progress in recent months" but that work remains to be done to "speed up the launching of the site." The Russian-Iranian team was "approaching the final stage" before the plant becomes operational, he said. Aghazadeh, who was accompanying Kiriyenko, said the test was going well and that engineers told him they expected no problems. "Today was one of the most important days for the Iranian nation," Aghazadeh said. "We are approaching full exploitation of this plant." In Jerusalem, Foreign Ministry spokesman Yigal Palmor said, "Iranians are showing again that they are making progress in their nuclear race." "This should be understood as very bad news for the whole of the international community," Palmor said, calling for "immediate and very determined steps in order to prevent Iran from becoming a nuclear power." AP contributed to this report.