President Bush, warning against the “foolish delusion” of negotiating with terrorists and dictators, has set off a foreign policy debate that is likely to color the rest of the presidential race.

Although White House officials denied that Mr. Bush had Senator Obama in mind when he quoted a pre-World War II lawmaker to illustrate the “false comfort of appeasement,” Mr. Obama accused the president of launching a “false political attack” against him because he has come out in favor of talks with rogue nations. Senator McCain and supporters such as Senator Lieberman, meanwhile, said Mr. Bush was correct in his speech yesterday to the Israeli Knesset.

As Israelis marked the 60th anniversary of their country’s founding, Secretary-General Ban expressed sympathy yesterday for the Palestinian Arabs, describing the birth of the Jewish state as a naqba, or catastrophe. Asked by The New York Sun whether senior U.N. officials had ever used the word, which Israelis view as an illegitimate term created for “propaganda” purposes, Mr. Ban’s aides were unable to cite any previous occasions.

On a visit to Masada earlier in the day with Prime Minister Olmert, Mr. Bush promised that the fortress, where the Jews lost their homeland more than 2,000 years ago, “shall never fall again.” Later, at the Knesset, he said, “Some seem to believe that we should negotiate with the terrorists and radicals, as if some ingenious argument will persuade them they have been wrong all along.

“We have heard this foolish delusion before,” Mr. Bush said. “As Nazi tanks crossed into Poland in 1939, an American senator declared: ‘Lord, if I could only have talked to Hitler, all this might have been avoided.’ We have an obligation to call this what it is — the false comfort of appeasement, which has been repeatedly discredited by history.”

Mr. Obama has been criticized by Republicans and his opponent for the Democratic presidential nomination, Senator Clinton, for his stated willingness to unconditionally negotiate with President Ahmadinejad of Iran. The Illinois senator has also said he would sit down with the dictators of Cuba, North Korea, and Venezuela, though in recent days he has highlighted his longtime objection to talks with the terrorist groups fighting Israel, such as Hamas.

The quotation that Mr. Bush cited has been used before to underscore the follies of isolationism and appeasement. The syndicated columnist Charles Krauthammer has ascribed it to a leader of the prewar isolationist movement, Senator William Borah, a Republican widely known as “the lion of Idaho.”

Mr. Obama and his supporters denounced the use of the Israeli holiday for what they said were political purposes.

“It is sad that President Bush would use a speech to the Knesset on the 60th anniversary of Israel’s independence to launch a false political attack,” Mr. Obama said in a statement. “George Bush knows that I have never supported engagement with terrorists, and the president’s extraordinary politicization of foreign policy and the politics of fear do nothing to secure the American people or our stalwart ally Israel.”

The White House said the senator’s quick response indicated a thin skin. “There are many who have suggested these types of negotiations with people that the president, President Bush, thinks that we should not talk to,” press secretary Dana Perino told reporters in Jerusalem. “I understand when you’re running for office you sometimes think the world revolves around you. That is not always true. And it is not true in this case.”

Mr. McCain, the presumptive Republican nominee, immediately engaged in the debate. “It does bring up an issue that we will be discussing with the American people, and that is: Why does Barack Obama, Senator Obama, want to sit down with a state sponsor of terrorism?” he told reporters on his campaign bus. “I think that Barack Obama needs to explain why he wants to sit down and talk with a man who is the head of a government that is a state sponsor of terror, that is responsible for the killing of brave young Americans, who wants to wipe Israel off the map, denies the Holocaust.”

At the United Nations, Mr. Ban called the president of the Palestinian Authority, Mahmoud Abbas, “on the occasion of the Palestinian commemoration of the Nakba, to underline his support for the Palestinian people,” a U.N. spokeswoman, Michele Montas, said. She added that last week Mr. Ban called Mr. Olmert to congratulate him on Israel’s Independence Day.

“We asked for a clarification of the spokeswoman’s statement,” an Israeli ambassador to the United Nations, Daniel Carmon, said. “The word ‘naqba,’ used to negate the legitimacy of the establishment of the state of Israel, is a tool of Arab propaganda. It should not be part of the U.N.’s vocabulary.”

No Palestinian Arab state can be established as long as the Palestinians define the founding of Israel as a catastrophe, Foreign Minister Tzipi Livni told a conference yesterday in Jerusalem. “The Palestinians could celebrate Independence Day if they would erase the word ‘naqba’ from their lexicon,” she said.