The White House said it was ready to "take action" against any threat to America as it indicated serious consideration of U.S. military strikes against Islamic State militants in Syria.

The Pentagon has warned of the dangers of IS and said operations against it in Syria may be needed, after weeks of air strikes have slowed the advance of the Sunni militant group in Iraq and as the West reeled from the grisly killing of American journalist James Foley.

President Barack Obama calls the Islamic State a jihadist "cancer" threatening the Middle East and the rest of the world but has so far backed only limited air strikes against the extremists.

If the United States intends to decisively defeat IS, what diplomatic and military means would be needed to crush them?

Vice President Joe Biden said Friday the United States would back a federal system in Iraq, as he pressed for unity in the sharply divided country amid a growing terror threat.

Writing in a Washington Post opinion piece, Biden said the United States was ready to "further enhance" its support of Iraq's fight against the Islamic State, and would urge its international partners to do so as well.

Morocco said on Friday it had arrested two Islamic State jihadists who had been planning to leave for IS training camps in Syria and Iraq to prepare attacks at home.

The two, whose identities were not disclosed, "planned to receive military training" before taking action in Morocco, "under the Islamic State's plans to expand its field of operations," an interior ministry statement said.

The United States imposed sanctions Friday on two Islamic extremists it accuses of ties to al-Qaida and the al-Nusra Front, alleging they financed and acted on behalf of the terror groups.

Under a designation issued by the U.S. Treasury, any assets the men -- Saudi and Kuwaiti nationals -- hold under U.S. jurisdiction are frozen and Americans are "generally prohibited from doing business with them."

From the rescue plane which took them on a one-way journey to France, two Iraqi refugees revealed tales of rape and fear at the hands of Islamic State that forced them to flee their homeland with nothing.

Rene, who did not want to give his last name, said the Islamic extremists currently rampaging through Syria and Iraq were as terrifying as they were sophisticated in their communication methods.

Britain will not work with Syrian President Bashar Assad to combat Islamic State (IS) fighters in the country and his permission would not be needed for any military intervention, Foreign Secretary Philip Hammond said Friday.

Hammond also said Britain had no plans to arm moderate fighters in Syria's civil war, and insisted that Western troops on the ground in Iraq would only make the situation worse.

At least 70 Islamic State jihadist fighters have been killed in 48 hours of clashes with Syrian army troops in the northern province of Raqa, a monitoring group said Friday.

Australia and Singapore vowed Friday to enhance intelligence sharing in the face of growing fears about the threat posed by jihadist citizens returning home after fighting in Syria and Iraq.

More than 191,000 people have died in Syria, U.N. rights chief Navi Pillay said on Friday, lashing out at "international paralysis" on the nearly three-and-a-half year conflict.

The South African, who wraps up a six-year stint as head of the UNHCR at the end of this month, has criticized world leaders for their lethargy on a wide range of conflicts.