The new red line comes as violence in eastern Ukraine has increased with the fledgling government in Kiev struggling to subdue pro-Russian separatists. Western powers say Moscow is behind the insurgents and has broken its promise to urge them to stand down.
Talk of the U.S. and European response to the continuing
Revelations that U.S. intelligence agencies listened in on Merkel's phone calls have caused sustained tensions between Berlin and Washington. Attempts to craft a new agreement outlining the rules of the road for spying between U.S. and Germany have so far failed.
Obama sought to reassure German citizens that the U.S. is not vacuuming up all of their phone conversations and email correspondence, saying, "Ordinary Germans are not subject to continual surveillance." He also pushed back on reports that the U.S. had offered and then rescinded a "no-spy agreement" to the French, which has angered Germans who have sought similar assurances.
The president also commented on a domestic controversy: the botched execution of a convicted murderer in Oklahoma. The incident has prompted a state investigation into death penalty procedures.