It’s too early to say for sure, but Secretary of State John Kerry appears to have achieved an important breakthrough in negotiating an end to the election impasse which imperils Afghanistan’s future. Abdullah Abdullah, who finished first in the initial round of voting and appears to have lost the runoff to Ashraf Ghani, has been screaming fraud and threatening to declare himself president on his own authority.

This is probably a bluff, but it’s a dangerous one because it threatens to reopen the deep fissures that fractured Afghanistan in the 1990s when Abdullah’s Northern Alliance, composed of Tajiks, Uzbeks and other ethnic minorities, fought a vicious civil war against the Taliban, whose ranks were (and are) made up of Pashtuns from the south and east. Ghani, who according to preliminary results won 56 percent of the vote, compared to Abdullah’s 44 percent, isn’t backing down either. He sees himself as the rightful next president of Afghanistan.

Enter Kerry. He flew into Kabul and in 12 hours of nonstop talks managed to get Abdullah and Ghani, both closeted in separate rooms of the U.S. Embassy along with their advisers, to agree on an internationally supervised procedure to audit all 8 million votes cast–a suspiciously high number, given that only 7 million or so voted in the first round of balloting.

If the process goes off as planned, and if it results in the seating of a government that is seen as legitimate (both admittedly big ifs), Kerry will have achieved a major diplomatic victory–one that could prevent Afghanistan from sliding back into chaos. It will in fact be only his latest triumph in Afghanistan where he has had more luck than most American officials, even when he was still only a senator, in dealing with the difficult Hamid Karzai.

Why does Kerry seem more successful in Afghanistan than elsewhere–for example, in the Middle East, where he devoted so much energy to the Israeli-Palestinian “peace process” only to see another round of fighting break out between Israel and Hamas? Or in Ukraine where he has had little luck in getting the Russians to end their aggression by proxy?

The answers are pretty obvious but bear repeating. In Afghanistan Kerry has two advantages that he does not enjoy when negotiating with Iran or the Palestinian Authority or Russia: He has overwhelming American military force at his back and he has the luxury of dealing with actors who may have some differences but fundamentally share similar goals and outlooks.

Although their numbers are much reduced (and will fall further by the end of the year) the U.S. military still has more than 30,000 troops in Afghanistan, backed up by ample air power, making them the most formidable military force in the country. That gives any American diplomat a lot of leverage should he choose to use it.

Moreover, while Abdullah and Ghani bitterly disagree about which of them should be president, they are both widely seen as technocrats who want a democratic, Western-oriented, non-Taliban future for the country. That makes it possible, if not easy, for them to bridge their differences in the same way that union and corporate negotiators can do if led along by a skillful mediator.

Alas few if any of those preconditions exist elsewhere in the world, which makes it all the more mysterious that Kerry wants to expend so much energy on what are almost sure to be fruitless negotiations with adversaries who have no reason to reach agreement. He would be better advised to focus his efforts on mediating other disputes between relatively reasonable rivals, e.g., South Korea and Japan, rather than wasting his breathe trying to persuade the Iranians to give up their nuclear program or the Palestinians to give up their dream of eradicating the Jewish state.