US foreign policy expert Zbigniew Brzezinski says the United States should retaliate if Russia does not stop bombing its assets in Syria. Brzezinski, the national security advisor for former President Jimmy Carter, advised President Barack Obama to attempt to disarm the Russians if they keep attacking the CIA-trained militants in Syria. "The Russian naval and air presences in Syria are vulnerable, isolated geographically from their homeland," Brzezinski wrote in an article published by the Financial Times on Sunday. "They could be 'disarmed' if they persist in provoking the US."