DRESDEN, Germany  President Obama on Friday intensified his pledge to unlock the Middle East stalemate, sending an envoy next week to pursue his call for a two-state solution, as he toured a former concentration camp that he said served as a lesson to “be ever-vigilant about the spread of evil in our own time.”

The president met with Chancellor Angela Merkel of Germany on the contentious issues of detainees at Guantánamo Bay, the nuclear program in Iran and the global financial crisis. But he quickly moved to the next stop of a trip built on his biography, visiting the site of Buchenwald, not far from where his great-uncle helped liberate prisoners in World War II.

“To this day, there are those who insist that the Holocaust never happened  a denial of fact and truth that is baseless and ignorant and hateful,” Mr. Obama said. “This place is the ultimate rebuke to such thoughts, a reminder of our duty to confront those who would tell lies about our history.”

The poignant imagery, which was broadcast on television here, was intended to underscore what Mr. Obama had described the day before in Cairo as America’s “unbreakable” bond with Israel. His speech there, which also called for two states, angered some in Israel because of his forceful opposition to expanding existing settlements on the West Bank.