BRUSSELS, June 28 (Reuters) - Syria appears to have heeded a U.S. warning against staging any new chemical weapons attack as no such action has been launched, U.S. Defense Secretary Jim Mattis said on Wednesday.

"It appears that they took the warning seriously," Mattis told reporters flying with him to Brussels for a meeting of NATO defence ministers. "They didn't do it."

(Reporting by Phil Stewart, Ediitng by Angus MacSwan)

Keywords: MIDEAST CRISIS/SYRIA MATTIS