Barack Obama has said that the participation of five Arab nations in air raids against ISIL in Syria "makes it clear to the world this is not America's fight alone".
The US president on Tuesday promised to continue the fight, which he said was vital to the security of his country, the Middle East and the world.
"Once again, it must be clear to anyone who would plot against America and do Americans harm that we will not tolerate safe havens for terrorists who threaten our people," he said.
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He added the joint fight against ISIL would take time, and promised to build more international support for the effort.
The American-led coalition conducted more than 200 air strikes on Tuesday against roughly two dozen targets in northern and eastern Syria.
ISIL controls a vast stretch of territory spanning the Syrian-Iraqi frontier and are fighting to expand the boundaries of their self-declared Islamic "caliphate". The UN has accused the group of committing atrocities in both countries.
The US-led campaign against ISIL has met with mixed reaction from Syria's multitude of rebel brigades, many of whom have been locked in a deadly fight with ISIL since January. But the rebels' ultimate goal is to topple Syrian President Bashar al-Assad, while the US is focused on defeating the ISIL.
On Wednesday, the main Western-backed Syrian opposition group criticised the American-led air strikes for being limited to ISIL and other self-declared jihadists while leaving Assad's government untouched.
"We regret that the international community has come up with partial solutions to the Syrian conflict in which hundreds of thousands were killed or detained by the Assad regime,'' said Nasr al-Hariri, secretary-general of the Syrian National Coalition.
Besides ISIL, the raids also hit al-Qaeda's branch in Syria, known as the Nusra Front, which has fought against ISIL. Washington considers it a terrorist group that threatens the US.
Syria's ambassador to the UN, Bashar Jaafari, told Al Jazeera that his US counterpart, Samantha Power, had informed him on the strike in advance.
Obama said the US was proud to stand shoulder-to-shoulder with Bahrain, Qatar, Saudi Arabia, Jordan and the UAE in conducting the air raids.
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Jordan, Bahrain and the UAE said their air forces were involved in the strikes.
Jordan said it would "not hesitate to take further actions to target and kill terrorists who are trying to attack our country".
The strikes hit ISIL's training compounds and command centres, storage facilities and vehicles in its de facto capital Raqqa, and targets in Deir ez-Zour, Albu Kamal and Hasakah, according to US officials.
The UK-based Syrian Observatory for Human Rights reported that at least 70 ISIL fighters were killed and more than 300 wounded in Raqqa and the east.
Rami Abdurrahman, the head of the Observatory, said about 22 raids targeted Raqqa province in addition to 30 in Deir ez-Zour. A military air base in the town of Tabqa and the town of Tel Abyad on the border with Turkey were also targeted, the Observatory said.
Further west, the strikes hit the village of Kfar Derian, a Nusra Front stronghold.
Around a dozen Nusra Front fighters were killed, according to two activists based in nearby Aleppo, Mohammed al-Dughaim and Abu Raed. One of the group's best snipers, known as Abu Youssef al-Turki, was among those killed, al-Dughaim said.
Activists in Aleppo also reported that 11 civilians were killed as a residential building near a Nusra base was hit.
The US said on Tuesday it had no indication of civilian casualties but that assessments were under way.
Source: Al Jazeera and agencies