JERUSALEM -- Prime Minister Ehud Barak threatened last night to halt peace negotiations with Syria unless it restrains Lebanon's Hezbollah guerrillas, who fired a missile into an Israeli outpost in South Lebanon earlier yesterday, killing three Israeli soldiers.
"Israel will not be able to negotiate peace as long as the Syrians do not restrain the Hezbollah from acting against the Israeli army in the security zone," Barak said in a statement.
Israel launched airstrikes against suspected Hezbollah bases in southern Lebanon.
Yesterday's fatal attack followed the death of an Israeli soldier last week and a Hezbollah bombing Sunday that killed Col. Akl Hashem, the No. 2 commander in the South Lebanon Army, the Israeli-allied militia in southern Lebanon.
Besides the warning to Syria, Barak set the stage for a further escalation, declaring, "Whoever dares hit [Israeli] soldiers, or the SLA soldiers or the northern settlements shall pay a heavy price."
Iran-backed Hezbollah has been fighting Israel's occupation forces in southern Lebanon for 14 years. Syria, which has up to 40,000 soldiers in Lebanon and effectively controls the country, has found the guerrilla war useful in maintaining pressure on Israel for its own purposes.
Hezbollah reported last week that its top leader, Hassan Nasrallah, had met in Damascus with Bashar Assad, son and heir apparent to Syrian President Hafez el Assad.
Syria is not believed to exercise day-to-day control over Hezbollah, according to United Nations officials in southern Lebanon. A senior U.S. official said the Syrians might not be able to halt Hezbollah attacks without using force against the guerrillas.
Yesterday's attacks worsened the prospects for restarting Israeli-Syrian peace talks, which have been stalled for two weeks over each side's demands for concessions from the other.
Clinton administration officials, who have staked considerable prestige in bringing about a Syrian-Israeli peace after years of trying to bring the countries to the negotiating table, spent Sunday trying to prevent the South Lebanon conflict from heating up.
The Clinton administration condemned yesterday's Hezbollah attack.
Before yesterday, Barak had refrained from demanding any halt to the fighting as a condition to continuing talks with Syria, apparently out of concern that Syria would demand something in return.
The prime minister's shift reflected mounting political pressure in recent days. The drawn-out war in Lebanon has aroused strong Israeli opposition, and the country and parliament are divided over the price Barak seems prepared to pay for peace with Syria. Barak also is caught up in a scandal over the financing of his election campaign.
A government spokesman said Barak is not ready to call off the peace talks. "This does not yet mean we stop the negotiations," he said.
But Barak's statement said the "lack of an atmosphere of peace" makes it difficult to negotiate.
Until last week, Israel had gone five months without having a soldier killed in Lebanon, keeping its forces well protected and relying heavily on air power to strike at Hezbollah positions.
The turnabout spotlighted Hezbollah's intelligence capability and staff work in locating significant targets and growing operational skill, said Timur Goksel, a special adviser to the U.N. Interim Force in Lebanon. The observation post hit yesterday was considered to be well protected and an unlikely target.
"They're out to prove they can breach any Israeli security in South Lebanon," Goksel said.
Killed were Maj. Tidhar Tempelhoff, 23, and Sgts. Lior Niv, 21, and Tzahi Malcha, 21.
One Israeli soldier was critically wounded and three sustained moderate injuries.
There were conflicting accounts of yesterday's attack. An Israeli military official said guerrillas had fired a "very accurate" missile through the window of the outpost.
Hezbollah, in a statement, said "machine gun fire and rocket-propelled grenades rained down on the rampart, killing or wounding the enemy troops."
Equally striking was the attack Sunday that killed the SLA's Hashem, Goksel said, in which guerrillas entered an insular Christian village that is suspicious of strangers and penetrated security around Hashem.
Israel staged repeated airstrikes in South Lebanon yesterday; there were no reports of casualties.
Goksel warned against further escalation that would risk civilian casualties on both sides.
"A couple of rockets in the wrong places could change a lot of things in the Middle East," he said.
Sun staff writer Jay Hancock contributed to this article.