President Bush (search), grim-faced as he opened a European trip with a tour of former Nazi death camps, urged the world on Saturday never to forget Holocaust victims. "Mankind must come together to fight such dark impulses," he said.

Bush visited the Auschwitz (search) and Birkenau (search) extermination camps -- "a place where millions were murdered," he called them -- with his wife, Laura. During World War II, more than 1.5 million Jews and tens of thousands of other victims were killed in the two camps.

"The sites are a sobering reminder of the power of evil and the need for people to resist evil," a clearly shaken Bush told reporters afterward.

His voice rising, Bush declared, "May God bless the victims and their families and may we always remember."

Later, he was outlining his vision for a revitalized trans-Atlantic alliance that will emphasize humanitarian as well as military cooperation.

"He will talk about the great challenges that the international community faces," including poverty, hunger and AIDS, said Secretary of State Colin Powell, previewing the president's Saturday talk.

At Auschwitz, Bush was solemn as he emerged from a tour of the gloomy complex's gas chamber and crematorium into bright sunshine outside. Laura Bush placed a long-stemmed rose on a cast-iron gurney used for pushing bodies into the ovens.

The president also participated in a wreath-laying ceremony at a brick wall in a row of prison barracks, where thousands of prisoners were executed. Bush bowed his head briefly, then gave a sharp nod before turning to go inside the building.

After another wreath-laying at Birkenau, at the end of the railhead that once brought prisoners into the death camp, Bush patted his wife comfortingly on the back.

"The civilized world must never forget what took place on this site," he said standing alongside the destroyed remains of a crematorium there.

Bush periodically wiped tears from his eyes, exhaling deeply at one point as if to compose himself and later pulling out a handkerchief, as he and the first lady walked through the complex. Neither spoke much, with the crunching of gravel underfoot and the quiet narration from their tour guide almost the only sounds.

During a private part of the tour, Bush was shown tiny shoes that had belonged to babies, hair taken from Jewish women, suitcases of some of those brought to the camps to die and the cell once occupied by Nobel Prize laureate Elie Wiesel.

"So sad," he remarked, according spokesman Ari Fleischer.

"Thank you sincerely for the deeply moving tour," he wrote in the guestbook. "In dedicating your lives to preserving the memory of the Holocaust and the martyrdom of Poles, you honor all who are victims here. May your work inspire future generations to stand ever vigilant against the return of such unspeakable evil to our world. Never forget."

Bush arrived in Poland, the first stop on a seven-day trip to Europe and the Middle East, Friday night. He was welcomed at the airport by a Polish military cordon, the soldiers wearing feathered caps and olive green capes.

Bush was meeting later Saturday with Polish President Aleksander Kwasniewski, a staunch supporter of the Iraq war. Poland sent 200 troops to fight in the war and has pledged 2,000 peacekeepers. It is responsible for maintaining stability in one of three postwar Iraq sectors.

Poland is among the administration's "new Europe" allies. That Bush chose Krakow as the site for his speech on future U.S.-European relations, rather than some other European locale, had clear symbolic importance.

Administration officials also emphasized that the president did not intend to belabor sharp differences that surfaced with key allies over the Iraq war.

"We had a major disagreement with France, with Germany, with Russia, with other countries over the Iraq war. I think where they all are now, where we are, is, let's talk about the future," Powell told reporters Friday on Air Force One.

"You move on," he added.

Bush also planned a stopover in St. Petersburg, Russia, to meet with President Vladimir Putin and participate in celebrations honoring that city's 300th anniversary. On Sunday, he heads Evian, France, for a Group of Eight summit of world economic powers.

Early next week, Bush will meet in Egypt with Arab leaders, then is scheduled to preside over a three-way summit in Jordan with Israeli Prime Minister Ariel Sharon and Palestinian Prime Minister Mahmoud Abbas.

Powell said such a three-way summit would represent an important start toward adopting the U.S.-backed peace plan that envisions a Palestinian state by 2005.

"We've got responsible leaders who want to move forward. And it will be a step at a time, and it will take a long time. The issues are difficult, the tensions are great," Powell said. "The lack of trust is there, and we have got to rebuild trust and get the two parties started."

Bush was only the second American president to visit Auschwitz, about 50 miles from this southern Polish city. President Ford visited in 1975, while Poland was under communist rule.

The former death camp is now a museum. Its main gate bears this German inscription: "Arbeit macht frei" ("Work makes you free").