The White House on Thursday night condemned what it called the "horrific terrorist" twin bomb blasts that killed 41 people in Beirut on Thursday.
"Such acts of terror only reinforce our commitment to support the institutions of the Lebanese state, including the security services, to ensure a stable, sovereign, and secure Lebanon," national security council spokesman Ned Price said in a statement quoted by AFP.
Hezbollah, meanwhile, vowed to continue its fight against "terrorists" and warned of a "long war" against its enemies, meaning in this case the Islamic State (ISIS) jihadist group, which claimed responsibility for the blasts.
The two explosions, which were separated by minutes, took place in the Ain el Sikkeh area, next to the Burj el-Barajneh Palestinian "refugee camp," at a busy time in the evening when the streets were full of families gathering after work.
In addition to the 41 deaths, at least 200 were said to be wounded in the blasts.
Burj el-Barajneh is a stronghold of Hezbollah, and has been targeted by attacks various times in the past.
Hezbollah is currently targeted by ISIS and Syrian rebels as it fights alongside Iran in the Syrian civil war.
There were repeated car bomb attacks against Shi'ite districts of Beirut in recent years.