U.S. President Barack Obama will make a statement on Tuesday following airstrikes for the first time against the ISIS militant group in Syria, according to the White House.
Obama will speak at 10 a.m. EDT (1400 GMT) before departing the White House for New York City to attend the U.N. climate meeting, the White House said in an emailed statement.
A White House official, speaking on background, said Obama will address the latest strategy to counter Islamic State in Syria.
The U.S. Department of Defense's joint staff director of operations also will hold a press briefing on the operations in Syria at 11 a.m. EDT (1500 GMT), the Pentagon said in a statement.
The United States and Arab allies began bombing in Syria for the first time on Tuesday, pursuing a campaign against militants in a war at the heart of the Middle East. The United States has been bombing Islamic State targets in Iraq for weeks. Islamic State vowed revenge for the attacks in Syria.
"We're still assessing the effectiveness of these strike, but we believe we hit what we were aiming at," Rear Admiral John Kirby, Pentagon press secretary, said in an interview on MSNBC on Tuesday, ahead of Obama's statement.
Kirby said the more than 20 strikes targeted Islamic State as well as Khorasan, an al Qaeda-linked group. The strikes took aim at the groups' ability to command their forces, by targeting vehicles, depots and headquarter buildings and affecting their ability to resupply and train fighters, he said.
Kirby echoed earlier statements by the U.S. military, saying the United States, which conducted eight of the strikes against the al Qaeda affiliate and without Arab partners, had "good information that this group was in the final stages of planning an attack - an imminent attack - even against targets in Europe or the U.S. homeland."
Number of dead?
The airstrikes have killed at least 70 Islamic State fighters on Tuesday in north and eastern Syria, according to the Syrian Observatory for Human Rights.
Rami Abdulrahman, who runs the group that tracks violence in the war, said the death toll was likely to be much higher. "The information is the numbers are bigger than that," he told Reuters by telephone.
He was citing casualties in the provinces of Raqqa, Deir al-Zor and Hasakah in northern and eastern Syria. Abdulrahman said the total number of dead and wounded was at least 300.
The dominant Kurdish political group in Syria welcomed strikes and said on Tuesday that it wanted to coordinate on confronting the militant group.
"We look forward to coordinating with the (anti-Islamic State) coalition in the face of terrorism, which threatens all human values in the Middle East," Democratic Union Party leader Salih Muslim said in a statement.
It also said that the Kurdish town of Kobani in northern Syria was still at risk from Islamic State, whose attacks in the surrounding countryside have driven tens of thousands of Kurds across the border into Turkey.