At some point in this presidential campaign, we may have a real debate on foreign policy differences between the parties. That hasn't yet happened.

The candidates have sparred about experience. They have clashed on Iraq. But they're still dancing around the most central question: How do you balance force and diplomacy when trying to keep America safe?

Nothing illustrates the need for clarity more than the jousting over whether America should talk directly to the likes of Ra?l Castro or Mahmoud Ahmadinejad.

In a July debate, Sen. Barack Obama was asked if he would talk without preconditions to leaders of Iran, Syria, Venezuela, Cuba and North Korea. He responded, "I would." President Bush and Sen. John McCain have taken Mr. Obama to task on this one, as has Sen. Hillary Clinton.

Communing with Mr. Castro or Mr. Ahmadinejad makes sense only after addressing grievances at lower levels. Holding summit meetings prematurely can hinder progress by raising false expectations.

"Having your picture taken with a tyrant such as Ra?l Castro lends ... the status of our country to him," President Bush said last week. It could also "discourage reformers inside their own country."

That said, the Bush policy of avoiding diplomacy in favor of military solutions has been a failure.

So, while Mr. Obama's readiness to meet dictators betrays inexperience, the essence of his (and Mrs. Clinton's) position is the right one. America's security, and the U.S. military's new counterinsurgency theory, will rely heavily on diplomacy and political maneuvers in the future, backed up by force only if unavoidable.

On this most central of issues, Mrs. Clinton has it right, and Mr. Obama grasps the essence. Mr. Bush and Sen. John McCain have it dead wrong.

Take Cuba. The point isn't, or shouldn't be, whether to hold a meeting with Ra?l Castro. It's whether it still makes sense to isolate and sanction Cuba. This policy, long after the Cold War's end, is dumb, a product of pandering to a segment of Florida voters. Mr. Bush and Mr. McCain support a policy that kept Fidel Castro in power for decades and will keep his brother in power, too.

Or take Iran. Here, too, proposing direct talks with Mr. Ahmadinejad is a mistake. The Iranian president heads the hardest-line faction in Tehran and shows little interest in better U.S.-Iranian relations. Iranians would regard such a summit as vindication for his anti-American and anti-Israel policies. Such a summit would undercut the more pragmatic factions in Iran.

In Tehran, there is still an internal power struggle over whether to engage fully with the Great Satan. So any U.S. diplomacy must be smart.

However, Mr. Obama was right when he said: "The notion that not talking to countries is punishment for them, which has been the guiding diplomatic principle of this administration, is ridiculous."

To exit Iraq, the United States must involve Iran in serious regional negotiations with all of Iraq's neighbors. This won't happen so long as Iran's top leaders still suspect America wants to topple their regime.

The next U.S. president needs to propose that America and Iran compile an agenda of their key concerns and discuss them without preconditions. Iran's threats to Israel, the nuclear issue and Iranian human rights violations would all be on that agenda. The aim would be to develop a new relationship that met the interests of both sides. Such a proposal would galvanize the pragmatists in the Iranian government.

Mr. Obama's tactics may betray inexperience, but he grasps the need to revamp U.S. policy toward Iran and Cuba. For all their "experience," Mr. Bush and Mr. McCain are glued to policies that have failed.

Trudy Rubin is a columnist for The Philadelphia Inquirer. Her column appears Tuesdays in The Sun. Her e-mail is trubin@phillynews.com.