The United States said it was ready to "take action" against any threat to America as it indicated serious consideration of US military strikes against ISIL in Syria.

The United States said it was ready to "take action" against any threat to America as it indicated serious consideration of US military strikes against ISIL in Syria.

The White House said late Friday that air strikes in Syria may be necessary, as deputy national security advisor Ben Rhodes agreed that "any strategy to deal with the ISIL organization has to deal with both sides of the border, Iraq and Syria."

"If we see plotting against Americans, we see a threat to the US emanating from anywhere, we stand ready to take action against that threat," Rhodes added.

"We've made very clear time and again that if you come after Americans, we're going to come after you wherever you are, and that's what's going to guide our planning in the days to come."

Earlier, the Pentagon has warned of the dangers of ISIL and said operations against it in Syria may be needed, after weeks of air strikes against the Takfiri militant group in Iraq and as the West reeled from the grisly killing of American journalist James Foley.

A US military official also told the Wall Street Journal that strikes at so-called "high-value targets," such as individual leaders, could be mounted within "an hour, it could be a week."

"If it's based on training camps, we could do that pretty soon."