US will act against Islamic State in Libya if needed -White House

"If there is a need for the United States to take unilateral action to protect the American people, the president won't hesitate to do that," White House spokesman Josh Earnest told reporters.

Earnest declined to comment on whether Obama had made any decisions on the possibility of sending ground troops into Libya, but said the president has "demonstrated a willingness to take decisive action," even in Libya.

Islamic State forces have attacked Libya's oil infrastructure and established a foothold in the city of Sirte, exploiting a power vacuum in the country where two rival governments have been battling for supremacy.

Libya's two warring administrations are expected to form a unity government.

Earnest said the United States would support the unity government on a range of national security measures, but it was too early to say what form that assistance would take.

"The more that we can bolster the capacity of the national unity government to govern that country, the better off we will be," he said. (Reporting by Roberta Rampton; Editing by Mohammad Zargham and Richard Chang)