Any US retaliation to Iran's missile attacks on American-targets in Iraq could lead to an all-out-war in the Middle-East, an adviser to Iranian-President Hassan Rouhani tweeted. "Any adverse military action by the US will be met with an all-out war across the region. The Saudis, however, could take a different path they could have total peace!" Hessameddin Ashena said in a statement on Twitter.