George Mitchell said the incident in which nine people died on a flotilla trying to break through an Israeli blockade on the Hamas-ruled Gaza Strip, showed the need for progress in talks he is mediating that got under way last month.
"This incident underscores to need to make progress in negotiations," said Mitchell in the West Bank town of Bethlehem.
Mitchell held talks on Wednesday with Palestinian President Mahmoud Abbas in the West Bank.
In a meeting later with Israeli Defense Minister Ehud Barak in Tel Aviv, the Israeli leader said he hoped Mitchell could "give renewed momentum" to the talks.
"We really expect and want to see that the recent event will not disturb the main course of our common policy to make sure that the peace process continues and doesn't stop," Barak said.
