U.S. and Russian air forces held a joint training exercise in Syria Tuesday as part of a larger effort to share intelligence and work together to combat terror groups amid a four-year-long civil war. Russian news media also reported Tuesday that Russia and Israel were informing each other continually on the situation in Syrian airspace. Few details were known about the joint training exercise, Reuters reported.

As officials in Washington and Moscow have inched closer toward working in unison to negotiate a new reality in Syria, a Russian foreign ministry spokeswoman said Tuesday that it was not a priority to keep Syrian President Bashar Assad in power. The U.S. and other Western nations have called for Assad to step down, and accused Russia of protecting Assad by targeting anti-Assad groups since starting airstrikes in Syria on Sept. 30.

Asked about protecting Assad's political future, Russian foreign ministry spokeswoman Maria Zakharova said on the Ekho Moskvy radio station Tuesday: "Absolutely not, we've never said that." "What we did say is a regime change in Syria could become a local or even regional catastrophe," she said, adding that "only the Syrian people can decide the president's fate." 

Russia announced in September it would carry out airstrikes aimed at Islamic State group fighters in Syria at Assad's request. The Russian defense ministry said Tuesday Russia's air force had flown 1,631 sorties and struck 2,084 militant targets since the start of the  campaign. Meanwhile, Deputy Foreign Minister Mikhail Bogdanov said Moscow would host a round of talks between Syrian officials and opposition leaders next week.

Iran, Russia's ally in Syria, has insisted that Assad stay in power. Russia "may not care if Assad stays in power as we do," the head of Iran’s Revolutionary Guard Corps, Major General Mohammad Ali Jafari, said Monday. He added: "We don't know any better person to replace him."

Diplomats representing the United States, its Gulf allies and Turkey meet in Vienna Friday to discuss efforts in Syria, but failed to reach agreement on Assad.