Several transport planes carrying military aid for the Lebanese army from the US and its Arab allies have arrived at Beirut airport.
Thousands of Palestinian refugees are still trapped inside the camp
The move follows an appeal for such aid by the Lebanese government.
Its forces are battling Islamist militants who have taken over the Nahr al-Bared Palestinian refugee camp in northern Lebanon.
US Secretary of State Condoleezza Rice has reiterated Washington's support for the Lebanese government.
She said gunmen in Nahr al-Bared were trying to destabilise a democratic government.
A Red Cross food convoy from the Jordanian capital, Amman, is travelling overland through Syria and is expected in northern Lebanon later on Friday.
The transport planes have come from US bases in the region as well as several Arab allies of the US in the Middle East.
The military supplies are believed to include ammunition for automatic rifles and heavy weapons, spare parts for military helicopters and night-vision equipment.
Reports from the area talk of sporadic gunfire exchanges between government troops and Fatah al-Islam fighters as the Lebanese army continues to build up around Nahr al-Bared, near the port city of Tripoli.
Thousands of people have fled the camp as aid workers struggle to deliver food and medicine to thousands still inside.
Lebanese Prime Minister Fouad Siniora has vowed not to "surrender to terrorism".
He said he would end the conflict "without hesitation" and described Fatah al-Islam as a criminal gang hiding behind Islam and the Palestinian cause.
The BBC's Jon Leyne, reporting from close to Nahr al-Bared, says the Lebanese army is in position in force outside the camp; inside, the militants are determined not to surrender.
At least 50 soldiers and militants have been killed in the fighting at the camp so far. The civilian death toll is not known.
The fighting at the camp is the bloodiest internal conflict in Lebanon since the civil war ended 17 years ago.
It began after security forces raided a building in Tripoli to arrest suspects in a bank robbery. Fatah al-Islam militants then attacked army posts at the entrances to the camp.
A large force of Lebanese troops hit back, bombarding the camp and storming a building on the outskirts of Tripoli.
Fatah al-Islam is a radical Palestinian splinter group alleged to have links with al-Qaeda. Lebanese officials also believe it is backed by Syria.
Other Palestinian factions have distanced themselves from the group, which emerged last year.