WASHINGTON -- Should the next president sit down with the leaders of Iran, or North Korea, just to chat?
Around that question revolves one of the few national security disagreements between Sens. Hillary Rodham Clinton and Barack Obama as they struggle to define themselves in advance of Tuesday's Democratic primaries in Maryland and elsewhere.
On other issues - the war in Iraq, nuclear proliferation, defense spending - it's difficult to see much daylight between the two.
Both say they would, as president, accelerate the troop withdrawals from Iraq. Both say they would leave some troops there, but neither has said how many or for what purpose.
"Nearly all of them should be out within a year," Clinton said in their most recent debate Jan. 31.
Obama declared in that debate that "I will end this war. We will not have a permanent occupation." But he also said that the United States will "need to have a strike force that can take out potential terrorist bases that get set up in Iraq."
Perhaps Clinton summed up their positions on Iraq most concisely: "There are no good options here. We have to untangle ourselves and navigate through some very treacherous terrain."
A sharper difference emerged early in the campaign on July 23, when Clinton and Obama had to face this debate question:
Would you meet separately, without preconditions, with the leaders of North Korea, Iran, Syria, Cuba and Venezuela in order to bridge the gaps that divide our countries?
No way, said Clinton.
Absolutely, said Obama.
"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 said.
Presidents John F. Kennedy and Ronald Reagan met with leaders of the Soviet Union, Obama said. "They understood that we may not trust them, they may pose an extraordinary danger to this country, but we have an obligation to find areas where we can potentially move forward."
But Clinton, in that July debate, stood her ground. "I will promise a very vigorous diplomatic effort," she explained. But "I don't want to be used for propaganda purposes. ... I will use a lot of high-level presidential envoys to test the waters, to feel the way."
No presidential meetings should be held "until we know better what the way forward would be," she said.
How to interpret these two stances?
"It may be that Obama thinks he can talk these guys into something," said Michael Mandelbaum, director of the American foreign policy program at the Johns Hopkins School of Advanced International Studies.
The risks of that approach appeared at a 1986 summit meeting between Reagan and Soviet Premier Mikhail S. Gorbachev in Reykjavik, Iceland. Reagan set aside a careful agenda and impulsively offered to do away with all ballistic missiles. The deal floundered when Gorbachev refused to endorse the deployment of missile defenses as Reagan wanted.
"It's very naive to think that having a meeting is going to cure some conflict that has fundamental causes," said Peter Rodman, a diplomat who was at the Reykjavik summit and who has served under Richard M. Nixon, Gerald R. Ford, Reagan and both Bushes.
"We and the Iranians understand each other very well. They see us as the obstacle to everything they're trying to achieve in the world - and they're right; and we see them as the problem in the same way," Rodman said. "That's not going to be fixed by a conversation."
Nor is the prestige of the White House to be spent casually.
"There are a lot of ways to talk to someone - back channels, intermediaries," said Ruth Wedgwood, professor of international law and diplomacy at Johns Hopkins and Yale Law School.
But appearing with a volatile guest, such as Iranian President Mahmoud Ahmadinejad, could backfire.
"Imagine Ahmadinejad coming to a state dinner, then holding a press conference to denounce the `Zionist conspiracy'," said Wedgwood. The president would have to denounce such remarks, which would exacerbate the tensions.
Successful summit meetings, even those held without explicit preconditions, rest on solid preparation, or at least a reasonable expectation of what can be achieved.
But diplomatic experts say there is still a place in international relations for the grand gesture - with careful preparation.
Perhaps the most famous "no preconditions" diplomacy was initiated by Egyptian President Anwar el Sadat in 1977, when he offered to fly to Israel to negotiate a peace treaty.
One risk in such ventures is that, while an ambassador can safely stall at awkward moments in negotiations by saying he has to check with the president, having a president actually in the room leaves little room for such finesse. "If the president makes a commitment, there's no retreat from that," saidAlan Henrickson, director of diplomatic studies at Tufts University's Fletcher School.
Those who worry that even well-prepared meetings can go awry often cite the 1961 Kennedy-Khrushchev summit meeting in Vienna, which is said to have left Khrushchev believing Kennedy was a weak leader. Soon Khrushchev was testing the White House by installing nuclear-tipped missiles 90 miles offshore, in Cuba.
In a combination of the grand gesture and solid preparation, Nixon went to China in 1972 with the assurance that a historic rapprochement was already a done deal.
"It would be unwise for any president to say he would never meet with a foreign leader," said Henrickson. Setting rigid preconditions, he said, "is just denying ourselves potential influence."