diff --git a/Lib/sched.py b/Lib/sched.py
--- a/Lib/sched.py
+++ b/Lib/sched.py
@@ -83,8 +83,10 @@
         """Check whether the queue is empty."""
         return not self._queue
 
-    def run(self):
+    def run(self, async=False):
         """Execute events until the queue is empty.
+        If async is True executes the scheduled events due to expire
+        soonest (if any) and then return.
 
         When there is a positive delay until the first event, the
         delay function is called and the event is left in the queue;
@@ -114,6 +116,8 @@
             time, priority, action, argument = checked_event = q[0]
             now = timefunc()
             if now < time:
+                if async:
+                    return
                 delayfunc(time - now)
             else:
                 event = pop(q)