(CNN) -- It's too soon to say what steps the United States will take against ISIS in Syria, President Barack Obama said Thursday.
"I don't want to put the cart before the horse," Obama told reporters during a White House news briefing. "We don't have a strategy yet."
Obama said he's asked America's top defense officials to prepare "a range of options" about what the United States could do to go after ISIS in Syria, which he described as "a safe haven" for the Sunni extremist group that calls itself the Islamic State.
The President's remarks follow days of speculation about whether the United States had a plan to go after ISIS in Syria.
"We need to make sure that we've got clear plans, that we're developing them. At that point, I will consult with Congress and make sure that their voices are heard," Obama said. "But there's no point in me asking for action on the part of Congress before I know exactly what it is that is going to be required for us to get the job done."
The Washington Post on Thursday reported that journalist James Foley, who was decapitated by ISIS, was tortured during his captivity.
Specifically, Foley was waterboarded, the newspaper reported, citing unnamed sources familiar with the treatment of abducted Westerners.
Waterboarding is a controversial technique that was used by the U.S. in its war of terrorism. Waterboarding is a interrogation technique where water is poured over a cloth covering the subject's face, creating the sensation of drowning.
A senior U.S. official declined to confirm to CNN if the waterboarding claims are true, saying that such details would not be discussed out of sensitivity to the families of those still being held.
"As we have said, hostages held by ISIL are at risk every day they are in ISIL's custody, given what we know about the nature of this brutal group," the official said, using an alternate acronym for ISIS.
'We're not going to do that alone'
But the President made clear any plan to go after ISIS in Syria would take time and require a regional strategy. "We're not going to do that alone," he said.
The President said he was sending Secretary of State John Kerry to the region to work on building a coalition needed to face the threat of ISIS militants.
"Clearly, ISIL has come to represent the very worst elements in the region that we have to deal with collectively, and that's going to require us to stabilize Syria in some fashion," Obama said. "And stabilizing Syria means that we've to got get moderate Sunnis who are able to govern and offer ... a real alternative."
But that may prove to be problematic. Syria's ally, Russia, has repeatedly blocked attempts by the U.N. Security Council that call on President Bashar al-Assad to step down as part of an effort to end the civil war that has wracked the country for three years.
Among the options Obama said he requested from the U.S. military were plans to make sure ISIS does not overrun Iraq.
U.S. airstrikes in Iraq are working, he said.
"The terrorists of (ISIS) are losing arms and equipment," Obama said, and Iraqi and Kurdish forces are making inroads.
But "the idea that the United States or any outside power would perpetually defeat ISIS ... is unrealistic," Obama said, insisting that a strong, trusted Iraqi government is critical to ousting the Islamist terror group permanently.
ISIS claims mass execution in Syria
ISIS said Thursday that it has executed at least 250 Syrian soldiers at an air base in the northeastern city of Raqqa.
The group said on one of its official websites that it killed the soldiers Wednesday. It also claimed to have killed 600 government soldiers in the fight for the Tabqa air base since August 19.
The Syrian Observatory for Human Rights, meanwhile, reported that 200 Syrian soldiers and 346 ISIS fighters died in the fight for the air base, which was considered the military's last holdout in eastern Syria. Hundreds more were wounded, the London-based activist group said.
ISIS claims that a video it posted online Thursday shows Syrian soldiers being paraded through the desert in their underwear. Another video posted by Syrian activists purportedly shows bodies lined up on the ground.
Later, ISIS posted a video that it says shows captured Kurdish soldiers, known as Peshmerga, wearing orange clothing similar to that worn by by American journalists James Foley and Steven Sotloff in other videos posted by the militant group.
Three masked men appear to decapitate one of the orange-clad soldiers in front of a mosque in Mosul.
In the video, titled "A message with blood to the leaders of the America Kurdish alliance," ISIS demands that the Kurdish government withdraw its forces from areas where it is battling the group.
CNN could not independently confirm the claims or the authenticity of the videos.
Fighting flares near Mosul Dam
The videos come amid reports of fresh fighting between ISIS and Kurdish forces near Iraq's Mosul Dam and the burning of oil wells near the strategic town of Zummar.
The Peshmerga are battling the militants near the town, important because of its location to the main thoroughfare that connects Mosul to the Syrian border, as well as near the Mosul Dam and the strategic Ain Zala oilfield, which ISIS forces seized from the Kurds this month, said Faud Hussein, chief of staff for Kurdish regional President Masoud Barzani.
Torching the three oil wells that make up the Ain Zala oilfield is an apparent effort by ISIS fighters to try to interrupt a Peshmerga advance on ISIS positions, Hussein said.
The extent of the damage to the oil fields wasn't immediately known.
The fighting comes nearly two weeks after thousands of Peshmerga and Iraqi commandos ousted ISIS forces for control of the dam, a crucial facility that provides electricity for millions of people in Iraq.
Kurdish officials have credited U.S. airstrikes against ISIS with helping Peshmerga forces push back against the extremists, whose breathtaking gains and brutal tactics captured the attention of world leaders.
Chelsea J. Carter and Catherine E. Shoichet reported and wrote from Atlanta. Hamdi Alkhshali reported from Atlanta. CNN's Barbara Starr and Jim Acosta in Washington, Anna Coren in Irbil, Iraq, and Jethro Mullen in Hong Kong contributed to this report.