Russian and U.S. air forces held a joint training exercise in Syria on Tuesday, Russian news agencies reported, citing a general with Russia's armed forces.Interfax news agency also reported, citing General Andrei Kartapolov, that Russia and Israel were informing each other continually on the situation in Syrian airspace."The purpose of the test was to validate the safety protocols established the memorandum of understanding," a Pentagon official told Anadolu Agency, referring to a recent agreement signed between the two countries."The test was conducted in the skies of south central Syria and lasted about 3 minutes," said the official who spoke on the condition of anonymity. "This test was a prudent measure solely to ensure that, in the event coalition aircraft encounter a Russian aircraft during operations in Syria, one of the established and agreed upon modes of communication in the agreement functioned."Russia has been conducting air strikes against Syrian opposition, and terror organizations such as ISIS, in an effort to support Syrian President Bashar al-Assad, while the U.S.-led coalition air forces have been supporting the Syrian opposition and also targeting ISIS terrorists in Syria. Russia and the U.S. have been holding diplomatic talks to plan for a post-Assad era, in which Russia mostly has been rooting for a transition period which would include keeping Assad in power. However, keeping Syrian President Bashar al-Assad in power is not crucial for Russia, RIA news agency quoted Russian Foreign Ministry spokeswoman Maria Zakharova as saying on Tuesday.When asked if saving Assad was a matter of principal for Russia, Zakharova said: "Absolutely not, we never said that.""We are not saying that Assad should leave or stay," she added.Russia's Foreign Ministry added that views of Russia, U.S., Saudi Arabia partially agree on which parts of Syrian opposition can be part of Syria dialogue.However, Zakharova was also quoted saying that Assad's his fate should be decided by Syrian people. "I can confirm that Russia's position on resolving the Syrian (crisis) has not changed," she was quoted as saying by TASS news agency.Russia's Foreign Minister Lavrov also confirmed Tuesdat thay Moscow is interested in the Organization of Islamic Cooperation joining talks on Syria.