Saudi Arabia has pledged 3 billion US dollars (£1.8 billion) to Lebanon to help strengthen the country's armed forces and purchase weapons from France.
Lebanon's president Michel Sleiman made the announcement yesterday, calling it the biggest grant ever for the nation's military.
Mr Sleiman, who made the surprise announcement in a televised national address, did not provide any further details.
The Lebanese army has struggled to contain a rising tide of violence linked to the civil war in neighbouring Syria, a conflict that has inflamed sectarian tensions in Lebanon and threatened the country's stability.
"The Saudi king decided to give a generous, well-appreciated grant to Lebanon amounting to 3 billion US dollars for the Lebanese army, which will allow it to buy new and modern weapons," he said.
"The king pointed out that the weapons will be bought from France quickly, considering the historical relations that tie it to Lebanon and the military co-operation between the two countries."
Mr Sleiman said he hoped Paris would quickly meet the initiative, and help the Lebanese army with arms, training and maintenance.
French president Francois Hollande, who was in Riyadh yesterday for talks with Saudi King Abdullah, said that France would help if requested to do so.
"If there are demands that are addressed to us, we will satisfy them," he told reporters.
Fragile in the best of times, Lebanon is struggling to cope with the fallout from Syria's civil war.
That conflict has deeply divided Lebanon, and paralysed the country's ramshackle political system to the point that it has been stuck with a weak and ineffectual caretaker government since April.
It has also seen a wave of deadly bombings and shootings that have fuelled fears that Lebanon, which suffered a brutal 15-year civil war of its own that only ended in 1990, could be slowly slipping back toward full-blown sectarian conflict.
In a nod to those concerns, Mr Sleiman said in his address that "Lebanon is threatened by sectarian conflict and extremism," and said that strengthening the army is a popular demand.
The Lebanese army is generally seen as a unifying force in the country, and draws its ranks from all of Lebanon's sects. But it has struggled to contain the escalating violence in the country since the outbreak of the Syrian conflict.
The Saudi pledge appeared aimed, at least in part, at boosting the military in relation to Hezbollah.
Historically, the Lebanese army has been equipped by the United States and France.
Washington has provided hundreds of millions of dollars of military aid in recent years to Lebanon that has included armoured vehicles, weapons and training for the Lebanese army.
The US says the programme aims to strengthen Lebanese government institutions.
Lebanon's tenuous grip on stability was made clear on Friday, when a car bomb killed senior Sunni politician Mohammed Chatah, who had been critical of Syria and Hezbollah.
Mr Chatah, a Sunni, was affiliated with Mr Hariri's Western-backed coalition, which has been locked in a bitter feud with a rival camp led by Hezbollah.
Mr Hariri, whose own father was killed by a massive car bomb in 2005, has indirectly blamed Hezbollah for Mr Chatah's assassination.
After a funeral service inside Beirut's blue-domed Mohammed al-Amin Mosque, pallbearers carried Mr Chatah's casket to the adjacent funeral tent where he was buried next to Mr Hariri's father, Rafik.
Speaking later, Fouad Siniora, a former prime minister and ally of Mr Chatah, praised his late colleague as a voice of moderation, and promised those in the crowd that such political killings will not knock the Lebanese off their course.