Prodding the international community, President Barack Obama called Friday "for all of us to redouble our efforts" toward separate Israeli and Palestinian states. "The moment is now for us to act," he declared. Alongside German Chancellor Angela Merkel one day after his trip to the Middle East, Obama said, "The United States can't force peace upon the parties." But he said America has "at least created the space, the atmosphere, in which talks can restart." The president announced that he was sending special envoy George J. Mitchell back to the region next week to follow up on his speech in Cairo a day earlier in which he called for both Israeli and Palestinian leaders to give ground in the longtime standoff toward the elusive goal of peace. Fresh from visits to Saudi Arabia and Egypt, Obama said that while regional powers and the entire international community were going to have to help Israelis and Palestinians achieve peace, "ultimately the parties involved have to make the decision that the prosperity and security of their people are best served" by an accord. "I think the moment is now for us to act on what we all know to be the truth, which is each side is going to have to make some difficult compromises," he added. He renewed his call for Israel to halt settlement activity in the West Bank and follow through on such previously made commitments, adding: "I recognize the very difficult politics in Israel of getting that done and I'm very sympathetic to how hard that will be." He also pressed Palestinians anew to dial back anti-Israel rhetoric that is not constructive to the peace process. Obama said Palestinian President Mahmoud Abbas "has made progress on this issue, but not enough." "All of these things are going to take time. But I'm confident ... we are going to make some progress on it," Obama added. Merkel, for her part, promised to cooperate in her own right on this long-sought goal. She said the two leaders discussed a timetable for a peace process but did not elaborate. "I think that, with the new American government and the president, there is a truly unique opportunity to revive this peace process or, let us put this very cautiously, this process of negotiations," Merkel said. Touching on an issue that has strained the American-German relationship, Obama also said he didn't seek any commitments from Germany as the United States seeks to close the US prison at Guantanamo Bay, Cuba, and determines what to do with the terrorism suspects held there. Merkel said her country is prepared to "constructively contribute" to US closure efforts and said she was confident of eventually reaching a "common solution" on the prisoners' fate. On other matters, Obama said he's seen "some progress" in bringing stability to the world in the wake of the deep recession that has crisscrossed the continents in recent months, and said he and Merkel agreed that they must continue to "work very closely together" to restore stability. Addressing climate change, Obama also said "we're going to have to make some tough decisions and take concrete actions if we are going to deal with a potentially cataclysmic disaster." The two leaders spoke to reporters after meeting privately at a castle in this east German city and before Obama was to tour the Buchenwald concentration camp. In his Thursday speech in Egypt, Obama issued a scathing indictment of those who question the Holocaust, saying that to do so "is baseless, it is ignorant, and it is hateful." "Threatening Israel with destruction or repeating vile stereotypes about Jews is deeply wrong and only serves to evoke in the minds of the Israelis this most painful of memories while preventing the peace that the people of this region deserve," Obama added. It was a pointed message to Iranian President Mahmoud Ahmadinejad, who has expressed doubts that 6 million Jews died at the hands of the Nazis and who has urged that Israel be wiped from the map. On Friday, the US president added: "The international community has an obligation, even when it's inconvenient, to act when genocide is occurring." Obama is the first US president to visit Buchenwald, and the stop was personal. A great-uncle helped liberate a nearby satellite camp, Ohrdruf, in early April 1945 just days before other US Army units overran Buchenwald. Ohrdruf no longer stands. But Buchenwald's main gate, crematorium, hospital and two guard towers have been kept as a memorial. Accompanying Obama to the site was Elie Wiesel, a 1986 Nobel Peace Prize winner, author and Holocaust survivor, who as a boy was taken to Auschwitz, then to Buchenwald, where his father died in 1945 three months before liberation. Following the tour, Obama was flying to Landstuhl medical hospital for private visits with US troops recovering from wounds sustained in Iraq and Afghanistan. And he was ending the day in Paris - reuniting with his wife, Michelle, and daughters Malia and Sasha, who planned a brief holiday in the City of Light after commemorating the 65th anniversary of the Allies' D-Day invasion in France.