The United States will soon deliver additional weaponry to help bolster the Lebanese military as it faces a growing threat from Islamic militants amid the fallout from the civil war in neighboring Syria, the US ambassador said Thursday.

Ambassador David Hale said the deliveries come in response to a request from the Lebanese armed forces for emergency assistance after Islamic militants overran a Lebanese town near the Syrian border, killing and kidnapping soldiers.

Hale did not say when the munitions would arrive, nor did he provide a price tag for them, but he did say the new assistance it is part of Washington’s long-standing partnership with the Lebanese military. The US has provided more than $1bn in military assistance since 2006, including over $120m in training and equipment since October, he said.

That assistance dwarfs in comparison, however, to a $3bn pledge Saudi Arabia made in late December to help strengthen Lebanon’s armed forces. The grant stipulated that the military hardware must be purchased from France, although none of the money has yet been delivered.

Separately, former Lebanese Prime Minister Saad Hariri, who enjoys close ties with the Saudi monarchy, last week announced an additional $1bn grant from the kingdom to help the Lebanese army in its fight.

The military is generally seen as a unifying force in Lebanon, and draws its ranks from all of the country’s sects – Sunni and Shiite Muslim, Christian and Druse. But the armed forces have struggled to contain the escalating violence in the country since the outbreak of the Syrian conflict in 2011.

The latest and most dangerous spillover from Syria took place early this month when militants, some of them linked to the Islamic State (Isis), crossed into Lebanon and raided the border town of Arsal, about 90 kilometers (55 miles) from Beirut.

After five days of gunbattles, the militants withdrew from the town as part of a negotiated truce, allowing Lebanese troops to redeploy inside and restore security. Twelve soldiers are still missing along with an unknown number of policemen, all of whom are believed to be held by the gunmen.

Also Thursday, Lebanon’s chief military prosecutor charged a group of 43 Syrians, only 10 of them in custody, over the fighting in Arsal.

Lebanon’s state news agency said the prosecutor, Sakr Sakr, charged the group with belonging to armed terrorist organizations, carrying out terrorist attacks and seeking to control Lebanese territory. The Syrians also face charges of killing soldiers and civilians.

Among those in custody is Imad Ahmad Jomaa, a Syrian national whose arrest by the Lebanese army was said to be the trigger for the clashes in Arsal.

Jomaa had identified himself as a member of the al-Qaida-linked Nusra Front – one of the most powerful rebel groups fighting against Assad but security officials said he later pledged allegiance to the Islamic State group.

The suspects could face the death penalty, if found guilty.