President Shimon Peres wrapped up a two-day visit to Russia Wednesday, saying the Kremlin promised to reconsider the planned delivery of S-300 air defense missiles to Iran that Israel and the US fear could be used to protect Iran's nuclear facilities. Russian President Dmitry Medvedev made the pledge during their talks Tuesday in the Black Sea resort of Sochi, Peres said. A Kremlin spokesman wouldn't immediately comment on Peres's statement. Russia signed a contract in 2007 to supply the missiles to Iran, but has so far dragged its feet on delivering them. Israeli government sources said the fact Russia had not delivered the missiles over the last two years was no mean diplomatic achievement. According to the officials, while Jerusalem and Washington were pressing the Russians not to deliver the missile systems, Iran and key figures in Russia's military industrial complex were pushing hard for the delivery to take place. "This is important in terms of Russian prestige, since they made the sale, and also for economic reasons," one official said. "The diplomatic achievement is that it has been stopped for two years." While Foreign Minister Sergei Lavrov made a similar pledge to reassess the sale when he visited Israel earlier this year, the significance of Medvedev's statement now is that he is the president, and has the final authority on the deal. Israel and the United States fear that Iran could use the missiles to protect its nuclear facilities - including the uranium enrichment plant at Natanz or the country's first atomic power plant, which is being completed by Russian workers in Bushehr. That would make a military strike on the Iranian facilities much more difficult. Israeli and US officials have strongly urged Moscow not to supply the missiles, and the issue has been the subject of intense diplomatic wrangling for years. The S-300 is one of the most advanced multi-target anti-aircraft missile systems in the world, and has a reported ability to track up to 100 targets simultaneously while engaging up to 12. The S-300 system was first deployed by the USSR in 1979 and was designed to defend large industrial and administrative facilities and military bases, and to control airspace against enemy aircraft. It has a range of about 200 km. and can hit targets at altitudes of 27,000 meters. Iran already has Russian-made TOR-M1 surface-to-air missiles, but they have a shorter range than the S-300. Regarding Iran, Peres said that Medvedev "told me that Russia will not support an Iranian nuclear bomb under any circumstances. But he also mentioned that the Russian appreciation of what's taking place in Iran is different from the American one." Russian officials confirmed in March that a contract for the S-300 missiles had been signed with Iran two years ago, but a top Russian defense official said in April that no deliveries had been made yet. Analysts said that Moscow could be using the S-300 contract as a bargaining chip in its relations with the US and Israel. Peres also said Wednesday that Iran's efforts to develop advanced missiles strained ties between Washington and Moscow. In May, Iran test-fired a new missile with a range of about 1,900 kilometers - far enough to strike Israel, southeastern Europe and US bases in the Middle East. "If it wasn't for Iranian missiles, maybe [at least] one of the thorny questions between Russia and the US [would] disappear - the bases that the United States is building in Poland and the Czech (Republic)," Peres said in a reference to the previous US administration's plans to build anti-missile defense sites in Eastern Europe. Russia has strongly opposed the US plans as a threat to its security, dismissing Washington's claims that the defense system is aimed at countering a threat from Iran. President Barack Obama has ordered a review of the anti-missile defense plans, but reiterated the US insistence that the missile defense system would pose no threat to Russia.