BRUSSELS (Reuters) - NATO Secretary-General Jens Stoltenberg said on Friday that Syrian President Bashar al-Assad “bears full responsibility” for the U.S. airstrikes against an air base in Syria. “The Syrian regime bears the full responsibility for this development,” Stoltenberg said in a statement.  “Any use of chemical weapons is unacceptable, cannot go unanswered, and those responsible must be held accountable,” said Stoltenberg, who was informed by the U.S. defense minister that strikes would go ahead.  