May 20 (Reuters) - White House hopefuls Barack Obama and John McCain have sparred over whether U.S. presidents should meet with adversaries, in a clash that could help define the foreign policy debate ahead of the November U.S. presidential election.

But Washington has a long history of talking to its enemies and the differences between Republicans and Democrats may be less stark than some of the heated rhetoric suggests.

Following are comments by some U.S. political figures over engaging foes:

PRESIDENT GEORGE W. BUSH, speaking to the Israeli parliament on May 15:

"Some seem to believe we should negotiate with terrorists and radicals, as if some ingenious argument will persuade them they have been wrong all along. We have heard this foolish delusion before. As Nazi tanks crossed into Poland in 1939, an American senator declared: 'Lord, if only I could have talked to Hitler, all of 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."

DEMOCRATIC PRESIDENTIAL CANDIDATE BARACK OBAMA, an Illinois senator, was asked in a July 23, 2007, Democratic candidates' debate whether he would be willing to meet without precondition with the leaders of Iran, Syria, Venezuela, Cuba and North Korea during his first year in office.

"I would," Obama said. "And the reason is this, that the notion that somehow not talking to countries is punishment to them -- which has been the guiding diplomatic principle of this administration -- is ridiculous."

Obama has since emphasized that while he would not set preconditions for a presidential meeting with U.S. foes, there would be plenty of preparations at the staff level.

"What are George Bush and John McCain afraid of?" Obama said on Monday in Billings, Montana. "Demanding that a country meets all your conditions ... before you meet with them, that's not a strategy, it's just naive wishful thinking," he said.

REPUBLICAN PRESIDENTIAL CANDIDATE JOHN MCCAIN, an Arizona senator, has criticized Obama's stand, especially on talking with the Iranian leader.

"It is a serious error on the part of Senator Obama," McCain said on May 15. "It shows naivete and inexperience and lack of judgment to say that he wants to sit down across the table from an individual who leads a country that says that Israel is a stinking corpse, that is dedicated to the extinction of the state of Israel. My question is, what does he want to talk about?"

At a town hall meeting in Miami on Tuesday, McCain planned to highlight Cuba to further press his point, saying that a U.S. presidential meeting with Cuban leader Raul Castro would send "the worst possible signal to Cuba's dictators."

"I believe we should give hope to the Cuban people, not to the Castro regime," McCain was to say, according to speech excerpts released by his campaign.

U.S. DEFENSE SECRETARY ROBERT GATES, in a May 14 speech to the American Academy of Diplomacy, said: "We need to figure out a way to develop some leverage with respect to the Iranians and then sit down and talk with them."

"If there's going to be a discussion, then they need something, too," Gates added. "We can't go to a discussion and be completely the demander with them not feeling that they need anything from us."

Defense Department spokesman Geoff Morrell later said Gates was talking more about contact between private U.S. citizens and Iranians than government-to-government discussions.

"I can tell you there is absolutely no gap between the secretary's position on Iran and the president's position on Iran," Morrell said.

FORMER PRESIDENT AND NOBEL LAUREATE JIMMY CARTER, speaking to ABC News before his April 17 meeting with Hamas leaders in Egypt:

"I think there's no doubt in anyone's mind that, if Israel is ever going to find peace with justice concerning the relationship with their next-door neighbors, the Palestinians, that Hamas will have to be included in the process.

"I think someone should be meeting with Hamas to see what we can do to encourage them to be cooperative."

FORMER SECRETARY OF STATE JAMES BAKER, CO-CHAIRMAN OF THE IRAQ STUDY GROUP, speaking before the Senate on Dec. 7, 2006, in defense of the panel's recommendation that Washington engage Iran and Syria for help in stabilizing Iraq:

"What do we lose by saying, 'We're getting all of Iraq's neighbors together, we want you to come,' and if they say no, we show the world what they're all about?"

NANCY PELOSI, SPEAKER OF THE U.S. HOUSE OF REPRESENTATIVES, on April 2, 2007, on the eve of meeting with Syrian President Bashar al-Assad in Damascus:

"When we go there we'll be talking about the overarching issue of the fight against terrorism and the role that Syria can play to help or to hinder. We think it's a good idea to establish the facts, to hopefully build some confidence between us ... we have no illusions but great hope." (Reporting by Caren Bohan and David Morgan; editing by Mohammad Zargham)