US President Barack Obama and Canada\'s Prime Minister Stephen Harper discussed by phone their \"grave concern\" over the Syrian regime\'s use of chemical weapons against civilians near Damascus on August 21, the White House said Monday evening, Kuna reported. The White House statement added that both countries \"agree that the international norm against the use of chemical weapons is longstanding and universal, and the use of chemical weapons anywhere diminishes the security of people everywhere.\" \"We continue to call for a strong international response to reinforce the prohibition on the use of chemical weapons to send a clear message that this kind of atrocity can never be repeated,\" the statement said. Obama and Harper \"pledged to continue to consult closely on potential responses,\" it said.