WASHINGTON -- American fighter jets and drones continued to pound Islamic State militants in Iraq on Wednesday, and military planners weighed the possibility of sending a small number of additional U.S. troops to Baghdad, U.S. officials said, even as the insurgents threatened to kill a second American captive in retribution for any continued attacks.

The airstrikes came in the hours after militants released a gruesome video Tuesday showing U.S. journalist James Foley being beheaded and underscored President Barack Obama's vow Wednesday afternoon to continue attacks against the group despite its threats.

According to a senior U.S. official, the number of additional troops currently under discussion would be fewer than 300, but there has been no final decision yet by Pentagon leaders. Officials said that the forces were requested by the State Department and, if approved, would mainly provide extra security around Baghdad.

The 14 latest airstrikes were in the area of the Mosul Dam and were aimed at helping Iraqi and Kurdish forces create a buffer zone at the key facility. The strikes, which now total 84 since operations began, have helped Iraqi and Kurdish troops reclaim the dam from the insurgents.

The militants threatened to kill Steven Sotloff, an American journalist who is also being held captive, if the U.S. continued to conduct airstrikes.

The officials were not authorized to discuss the ongoing operations publicly and spoke on condition of anonymity.

It was not clear Wednesday if Obama would have to adjust his recent notifications to Congress under the War Powers Act to accommodate the higher U.S. troop level in Iraq if more soldiers and Marines are deployed.

There are about 748 U.S. forces in Iraq, in addition to the approximately 100 troops that have routinely been assigned to the Office of Security Cooperation in Baghdad. Under the current war powers resolutions sent to Congress, Obama authorized up to 775 U.S. troops for security assistance, assessment teams, and advisers at two joint operations centres in Baghdad and Irbil.

Foley, a 40-year-old journalist from Rochester, New Hampshire, went missing in northern Syria while freelancing for Agence France-Presse and the Boston-based media company GlobalPost. Officials have said the video appears authentic.

Released on websites Tuesday, the video shows a man in an orange jumpsuit kneeling in the desert, next to a black-clad militant with a knife to his throat. Foley's name appears in both English and Arabic graphics on screen.

After the captive makes a statement, the masked man is shown apparently beginning to cut at the neck of the captive.

At the end of the video, a second man -- identified as Sotloff -- is shown and the militant warns that he could be next captive killed. Sotloff was kidnapped near the Syrian-Turkish border in August 2013 and freelanced for Time, the National Interest and MediaLine.