U.N. Secretary General Ban Ki-moon on Monday appealed to the Security Council to act with "seriousness" on Syria, where he said the situation has become "unacceptable." "The situation has reached an unacceptable point," Ban said on the sidelines of an energy summit in Abu Dhabi. "I sincerely hope that the Security Council will handle this in a sense of seriousness and gravity and in a coherent manner,” he said. "I know there are some differences of opinions among member states of the Security Council, but the number of casualties has reached to such an unacceptable stage," Ban said. "We cannot let this situation continue like this."