US has strongly condemned the "senseless and despicable terrorist bombings" at the Iranian Embassy in Beirut.
On Tuesday, a double suicide bombing outside the Iranian embassy in Beirut killed at least 23 people and wounded almost 150 people, in an attack claimed by an al-Qaeda-linked jihadist group.
"We extend our condolences to the victims and their families. We urge all parties to exercise calm and restraint to avoid inflaming the situation further," US secretary of state John Kerry said.
"The United States knows too well the cost of terrorism directed at our own diplomats around the world, and our hearts go out to the Iranian people after this violent and unjustifiable attack claimed the life of at least one of their diplomats," he said.
Noting that the details of the attack are not yet clear, Kerry said the US supports Lebanon's commitment to conduct a thorough investigation.
"We call on all parties to cooperate with the Lebanese government?s investigation of this crime and urge that those responsible are brought to justice," he said.
"Acts of terror only reinforce our determination to support the institutions of the Lebanese state, including the Lebanese Armed Forces and the Internal Security Forces, to ensure a stable, sovereign, and secure Lebanon," Kerry said.