Russia appears ready to sell Venezuela the same five advanced S-300PMU-1 air defense missile battalions it withheld from Iran because of international sanctions. debkafile's military sources report Venezuela's ruler Hugo Chavez, offered to buy them when he met Russian President Dmitry Medvedev in Moscow Thursday, Oct. 14.  Israel immediately turned to Washington to try and block the transaction. Clearly, the highly-sophisticated interceptors are bound for their original client, Iran, through its good friend Chavez. This time, the deal will be much harder to stop.   Our military sources stress that Iran needs the S-300 as the key to the effective defense of its nuclear and strategic sites against air or missile attack - even by cruise missiles - and to raising the risk to the assailants of heavy casualties. That said, the Israeli Air Force has spent the last two years training intensively in tactics for countering those very Russian interceptors. In September, Israel and Greece carried out joint practice strikes against the S-300 missiles Athens had purchased from Moscow. Chavez began his Moscow visit by voicing interest in "buying different types of Russian-made air defense systems to create a multilayered air defense network." The day after his offer, Russia cautiously tested the water in Washington to find how the Obama administration reacted to the prospect of ballistic missile interceptors being deployed not only in Iran but in the United States' Latin American backyard. Igor Korotchenko, head of a Moscow think tank on the international arms trade, revealed: "Russia is looking for a buyer for five battalions of S-300PMU-1 defense systems ordered by Iran and Venezuela could become such a buyer." He knew enough about the deal to disclose that Caracas was prepared to pay the asking price of $800 million in cash to expedite the deal although it asked  Moscow for several loans to cover previous arms transactions, including the recent $2.2 billion purchase of 92 Russian T-72 tanks and the Smerch multiple launch rocket systems. Our sources add Iran rather than Venezuela is in a hurry to get hold of the missiles and install them around its most vulnerable sites. There should be no delay once they reach Tehran because special units of the Iranian Revolutionary Guards had finished training on the weapon's operation in Russia. debkafile's sources note that hardly a month has gone by since Sept. 22 when Medvedev publicly announced the S-300 missile system sale to Iran was cancelled - to wide acclaim from the US and Israeli media. Moscow lost no time in finding a neat stratagem for bypassing the UN sanctions barring arms sales to Iran with impunity. Even the Russian offer to return the $166.8 million Iran advanced for the deal can be covered by Caracas as intermediate customer