Rehn broke his vacation with a news conference in Brussels. He blamed poor communication for the drop in stock prices and said Italy and Spain are both basically doing well.
"We all in Europe will have to ensure rigor in our communications and sufficient verbal discipline so that we ensure our joint message will be listened to and understood in the way we want it to be understood," Rehn said. "If you look at so-called market forces, or market players and perceptions, what they are after -- they are after making money and that is driven by fear and greed."
He said his staff continues to work hard through the August vacation season.
Rehn defended Jose Manuel Barroso, the head of the European Commission, who suggested in a letter Thursday everything in the July 21 financial bailout agreement could still change.
"President Barroso's first and foremost objective with this letter was to speed up the implementation of the agreement of the 21st of July," he said.