Meanwhile, sporadic gunfire exchanges punctured the lull in the fighting as the Lebanese army continued to build up around the Nahr el-Bared refugee camp near the port city of Tripoli.
As flares illuminated the sky, heavy exchanges of gunfire were heard late on Friday between Lebanese troops and Islamic militants holed up inside the camp.
The military was gearing up for a fight, rolling more troops into place around the camp in northern Lebanon, already ringed by hundreds of soldiers backed by artillery and tanks. Fatah Islam has claimed to have more than 500 fighters, armed with automatic weapons, mortars and rocket-propelled grenades.
At least a dozen more armored carriers and a battle tank were seen headed for the area Friday.
Palestinian factions were scrambling to find a negotiated solution to end the siege, and Lebanese Defense Minister Elias Murr said he was "leaving room for political negotiations."
But he insisted on the surrender of the fighters from the Fatah Islam militant group inside the camp, telling reporters: "If the political negotiations fail, I leave it to the military command to do what is necessary." In a statement Friday, the military told the militants, "You have no choice but to surrender."
An assault could deepen splits between the government and the Hezbollah-led opposition. Shiite Hezbollah deeply opposes Sunni militant groups like Fatah Islam. But the Syrian- and Iranian-backed Hezbollah also accuses the government of Prime Minister Fuad Saniora of being in the pocket of the United States and is pushing for his ouster.
The airlift from the United States was a strong show of support for Saniora and could boost the military in what would likely be a tough urban battle inside the camp, a densely built town of narrow streets.
Amid the swell of international support, Saniora has vowed to wipe out Fatah Islam. In a televised address Thursday, he said that Fatah Islam was "a terrorist organization ... attempting to ride on the suffering and the struggle of the Palestinian people."
"We will work to root out and strike at terrorism, but we will embrace and protect our brothers in the camps," Saniora said, insisting Lebanon has no quarrel with the 400,000 Palestinian refugees living in the country.
Under a 1969 agreement, Lebanese military stays out of the camps that are run by the Palestinians.
But Abu Salim Taha, a spokesman for the militants, repeated late Thursday that Fatah Islam would never surrender or flee but "fight until the last moment, the last drop of blood and the last bullet."
Between late Thursday and early afternoon Friday, five military transport planes landed at Beirut's airport, including one from the U.S. Air Force, two from the United Arab Emirates and two from Jordan. Media reports said included they included ammunition, body armor, helmets and night-vision equipment.
U.S. military officials said Washington would send eight planes of supplies, part of a package that had been agreed on but that the Lebanese government asked to be expedited.
The U.S. airlift, however, brought criticism from Hezbollah, the government's top domestic opponent, whose leader warned that Lebanon was being dragged into a U.S. war against al Qaeda that would destabilize the country.
In a televised address, Hezbollah chief Sheik Hassan Nasrallah warned the military against assaulting the Nahr el-Bared refugee camp to uproot Fatah Islam, calling instead for a negotiated solution.
"Does it concern us that we start a conflict with al Qaeda in Lebanon and consequently attract members and fighters of al Qaeda from all over the world to Lebanon to conduct their battle with the Lebanese army and the rest of the Lebanese?" he asked.
Nasrallah called the aid "a dangerous thing."
"You all know that I have nothing to do with al Qaeda and you know al Qaeda's position toward us," he said, referring to Sunni al Qaeda's calls for the killing of Shiites. But, he added, addressing the government, "There is an American-al Qaeda conflict. Do you want to fight the others' war on our land?"
Nasrallah's resistance to an assault on the camp could complicate the government's campaign in the pursuit of the militants. While he may not be able to stop an offensive, his words carry political weight.
They also demonstrate the dangerous political and military straits of the Lebanese government is navigating in the crisis, as more troops took up positions around the camp for what could be a bloody battle against Fatah Islam — with thousands of Palestinian civilians caught in the crossfire.
On the military front, an assault could spark unrest and violence elsewhere in the country, where some 400,000 Palestinian refugees live, most in camps that are rife with armed groups. Fatah Islam warned it has "sleeper cells" in Lebanon that would carry out revenge attacks, and other Islamic militants have threatened terror bombings if the military attacks the camp.
About half of Nahr el-Bared's population of 31,000 fled the camp during the truce, flooding into the nearby Beddawi camp. At least 20 civilians and 30 soldiers were killed in the fighting earlier this week. The Lebanese military says 60 Fatah Islam fighters were killed, though the group put the toll at 10.
A deputy Fatah Islam leader, Abu Hureira, told the pan-Arab Al Hayat daily by telephone from Nahr el-Bared that "sleeper cells" in other Palestinian camps and elsewhere in Lebanon were awaiting word for a "violent response" if the army struck.
The U.S. military aid could also attract other militants into what they see as a battle against the West and its allies. Extremist groups were already using the battle at the camp as propaganda.
A group billing itself as al Qaeda's branch in Syria and Lebanon vowed "seas of blood" if the Lebanese army resumes its attack. In a video posted on the Web Friday, a spokesman for the group threatened bomb attacks on Lebanon's vital tourist industry. Earlier, a Palestinian group called the Army of Islam also threatened attacks. The capabilities of the two groups are not known.