Saudi Arabia is giving the Lebanese army $3 billion in aid, Lebanon's President Michel Suleiman said, calling it the largest grant ever given to the country's armed forces.
"The king of the brotherly Kingdom of Saudi Arabia is offering this generous and appreciated aid of $3 billion to the Lebanese army to strengthen its capabilities," Suleiman said in a televised address.
Lebanon's armed forces have been struggling to deal with violence spreading over the border from Syria's civil war.
The country, which is still rebuilding after its own 15-year civil war, has seen clashes between gunmen loyal to opposing sides of the Syrian conflict, as well as militant attacks on the army itself.
Lebanon's army is seen as one of the few institutions not overtaken by sectarian divisions that plague the country.
But it is ill-equipped to deal with internal militant groups, particularly the Shia Muslim guerrilla and political movement Hezbollah, which is funded by the regional Shia power Iran.
The Sunni Muslim kingdom of Saudi Arabia may be seeking to bolster the army as a counterbalance to Hezbollah, seen as the most effective and powerful armed group in Lebanon.
Rising regional Sunni-Shia tensions have been stoked by the fight in neighbouring Syria, which generally pits the country's majority Sunni Muslim rebels against President Bashar al-Assad's minority Alawite sect, an offshoot of Shia Islam.