JERUSALEM — A teary-eyed President Bush stopped in front of an aerial photo of Auschwitz today at Israel’s Holocaust memorial and said America should have sent bombers to prevent the extermination of Jews there.

Yad Vashem’s chairman, Avner Shalev, quoted Mr. Bush as saying America should have “bombed it.” Secretary of State Rice said Mr. Bush referred to the train tracks leading to Auschwitz, not the camp itself, where between 1.1 million and 1.5 million people were killed by Nazi Germany.

The issue of bombing the Nazi death camps or the rail lines leading to them has been debated for years — and the lack of action was interpreted by some as a sign of Allied indifference.

The Allies had detailed reports about Auschwitz toward the end of World War II from escaped prisoners. But they chose not to bomb the camp, the rail lines, or any of the other Nazi death camps, preferring instead to focus all resources on the broader military effort.

Some experts note only late in the war did America have the capability to bomb the infamous camp in occupied Poland, and also faced a moral dilemma since such an operation could kill thousands of prisoners. Even Jewish leaders at the time struggled with the issue and many concluded that loss of innocent lives under such circumstances was justifiable.

Mr. Bush twice had tears in his eyes during an hour-long tour of the museum, Mr. Shalev, who guided Mr. Bush, said.

Upon viewing an aerial shot of Auschwitz, taken during the war by American forces, he said Mr. Bush called the decision not to bomb it “complex.” He then called over Ms. Rice to discuss President Roosevelt’s decision, clearly pondering the options before rendering an opinion of his own, Mr. Shalev said.

Mr. Shalev quoted Mr. Bush as asking Ms. Rice, “Why didn’t Roosevelt bomb it?” He said Ms. Rice and Mr. Bush discussed the matter further and then the president delivered his verdict.

“We should have bombed it,” Mr. Shalev, speaking in Hebrew, quoted Mr. Bush as saying.

Briefing reporters later on Air Force One, Ms. Rice said Mr. Bush was talking about the rail lines to the camp.

“We were talking about the often-discussed ‘Could the United States have done more by bombing the train tracks?'” Ms. Rice said. “And so we were just talking about the various explanations that had been given about why that might not have been done.

“It was an exhibit about the train tracks. And so we were just talking about the various explanations because, you know, there are three or four different explanations about why the United States chose not to try to bomb the train tracks,” she said.

Ms. Rice did not detail those reasons.

Later tonight, asked about Ms. Rice’s remarks to reporters, Mr. Shalev said the president was not specific about what the Allies should have bombed.

A leading Israeli scholar of the Holocaust, Tom Segev, said Mr. Bush’s reported comment, which appeared spontaneous, marked the first time an American president had made this acknowledgment.

“It is clear now that the U.S. knew a lot about it,” Mr. Segev said. “It’s possible that bombing at least the railway to the camps may have saved the lives of the Jews of Hungary. They were the very last ones who were sent to Auschwitz at a time when everybody knew what was going on.”

At the dedication of the U.S. Holocaust Memorial Museum in Washington in 1993, Nobel Peace Prize laureate Elie Wiesel famously asked, “Why weren’t the railways leading to Birkenau bombed by allied bombers? As long as I live I will not understand that.”

At that same dedication, President Clinton said that the West has to “live forever with this knowledge … (that) far too little was done,” and that “rail lines to the camps within miles of militarily significant targets were left undisturbed.”

Mr. Segev said the question of a bombing was not so clear cut, noting that it wasn’t certain America had the ability to carry out such an operation.

In a response to a request that America forces bomb Auschwitz and the rail lines, Roosevelt’s assistant secretary of war, John J. McCloy, laid out the America rationale for inaction.

“Such an operation could be executed only by the diversion of considerable air support essential to the success of our forces now engaged in decisive operations elsewhere and would in any case be of such doubtful efficacy that it would not be warrant use of our resources,” he wrote in an August 14, 1944, letter.

A Holocaust scholar, Michael Berenbaum, said the photo presentation at the museum, and Mr. Bush’s reported comments there, do not reflect the difficulties in bombing Auschwitz.

“It would have been a much more complex decision than what is presumed here,” Mr. Berenbaum, who teaches at the American Jewish University in Los Angeles, said.

Mr. Berenbaum said the aerial photos that Mr. Bush saw at the museum were not developed from the negatives until 1977, nor were they taken purposely to depict Auschwitz. American intelligence forces took them during a bombing campaign on a German chemical plant nearby, which they carried out in August 1944.

But he also said there is no question that had the Allies been interested, they could have bombed Auschwitz and saved lives. By the time the idea was raised in summer 1944, they could have bombed the camp and the railway tracks leading to it using air bases in Italy or, if they had wanted to earlier, from Soviet territory.

“The Americans flubbed it,” Mr. Berenbaum said. “The bombing could have weakened the infrastructure and made it more difficult to kill with the efficacy with which they killed.”

In an article Mr. Berenbaum wrote for Encyclopaedia Britannica, he quoted Wiesel, who was a prisoner at Buna-Monowitz, the slave-labor camp of Auschwitz, as saying that inmates were “filled with joy” over the August 1944 Allied bombing of an adjacent plant. “We were no longer afraid of death; at any rate, not of that death,” he quoted Wiesel as saying.

The David S. Wyman Institute for Holocaust Studies in Washington issued a statement praising Mr. Bush’s reported remark.

“The refusal to bomb Auschwitz was part of a broader policy by the Roosevelt administration to refrain from taking action to rescue or shelter Jewish refugees during the Holocaust. Tragically, the United States turned away from one of history’s most compelling moral challenges,” the institute’s director, Rafael Medoff, said.

A professor of Jewish Thought at Israel’s Hebrew University, Eliezer Schweid, said the question of a bombing is irrelevant in retrospect.

World Jewish leadership “was afraid to ask publicly” for the Allies to bomb the death camps, believing that would turn the conflict into a war for the Jews, Mr. Schweid said.

Mr. Bush was accompanied on his tour by a small party that included Ms. Rice, Prime Minister Olmert and President Shimon Peres.

At the compound, overlooking a forest on Jerusalem’s outskirts, Mr. Bush visited a memorial to the 1.5 million Jewish children killed in the Holocaust, featuring six candles reflected 1.5 million times in a hall of mirrors.

At the site’s Hall of Remembrance, he heard a cantor chant a Jewish prayer for the dead. There, Mr. Bush, wearing a yarmulke, placed a red, white, and blue wreath on a stone slab that covers ashes of Holocaust victims taken from six extermination camps. He also lit a torch memorializing the victims.

“I was most impressed that people in the face of horror and evil would not forsake their God. In the face of unspeakable crimes against humanity, brave souls — young and old — stood strong for what they believe,” Mr. Bush said.

“I wish as many people as possible would come to this place. It is a sobering reminder that evil exists, and a call that when evil exists we must resist it,” he said.

The memorial was closed to the public and under heavy guard today, with armed soldiers standing atop some of the site’s monuments and a police helicopter and surveillance blimp overhead.

It was Mr. Bush’s second visit to the memorial. His first was in 1998, as governor of Texas. The last sitting American president to visit was Mr. Clinton in 1994.

In the visitors’ book, the president wrote simply, “God bless Israel, George Bush.”