BEIRUT -- When the Israeli-Syrian peace negotiations resumed in December, it was widely recognized that perhaps the greatest hazard they faced was the war of attrition between Hezbollah guerrillas and Israelis in occupied South Lebanon. The United States joined Israel in entreating Syrian President Hafez al-Assad to restrain the Iranian-backed Islamic resistance.

But Assad would have none of it, knowing that the pain inflicted on Israel in its Lebanese hell hole was a key reason why Israeli Prime Minister Ehud Barak was signaling his readiness for a peace settlement in which Israel not only got out of South Lebanon, but came down from the Golan Heights, too. Assad wanted to retain the ability to go on inflicting the pain until he had cast-iron guarantees that that would actually happen.

South Lebanon is a last, potent card in Assad's otherwise historically weakening negotiating hand. But it is a double-edged one. Given the overall imbalance of military power between the two adversaries, it can at any time be turned into a far more potent one in Israel's hand. Tel Aviv's second blitz on Lebanese power stations in seven months was dramatic illustration of that. It was also through the adroit use of this card, Barak said, that he persuaded Assad to come back to the negotiating table. He pledged to pull his army out of South Lebanon by July this year. That, paradoxically, was evidently more menacing to Assad than its staying. For after such a unilateral withdrawal, involving no agreement with Syria, Israel would have far less incentive to withdraw from the Golan.