Iran accused the United States Sunday of not taking the threat from Islamic State militants in Iraq and Syria seriously, and charged that U.S. aid had previously helped the jihadists.

Maronite Patriarch Beshara al-Rahi and the patriarchs of the Orient are expected to hold talks with U.S. President Barack Obama on the sidelines of a conference in Washington.

The conference, which will be held on September 9,10 and 11, aims at discussing the situation in the Middle East and the conditions of Christians, As Safir newspaper reported on Thursday.

An American fighting for the Islamic State was killed over the weekend in Syria, U.S. officials said Tuesday, underlining growing concerns about Westerners signing up for extremist groups in the Middle East.

U.S. President Barack Obama sent special operations troops to Syria this summer on a secret mission to rescue American hostages, including journalist James Foley, held by Islamic State extremists, but they did not find them, the administration disclosed Wednesday.

Officials said the rescue mission was authorized after intelligence agencies believed they had identified the location inside Syria where the hostages were being held. But the several dozen special operations forces dropped by aircraft into Syria did not find them at that location and engaged in a firefight with Islamic State militants before departing, killing several militants. No Americans died but one sustained a minor injury when an aircraft was hit.

U.S. aircraft pounded Islamic State militants in 14 air strikes near Iraq's largest dam in the past 24 hours, officials said Wednesday, amid IS threats to kill a second American journalist.

Since Tuesday, U.S. drones and fighter jets destroyed or damaged six IS Humvees, three sites for improvised explosive devices, one mortar tube and two armed trucks, U.S. Central Command said.

Washington and Damascus are "not on the same page" in the fight against their common enemy the Islamic State, whose militants have declared a "caliphate" straddling swathes of Iraq and Syria, U.S. officials said Monday.

The United States has sent 130 more military advisers to northern Iraq to assess the scope of the humanitarian crisis there, U.S. Defense Secretary Chuck Hagel said Tuesday.

The United States said Tuesday that it expects to participate in Cairo talks between Israelis and Palestinians aimed at securing a lasting ceasefire in Gaza.

The United States will screen delegates from Ebola-hit countries coming to Washington for an unprecedented U.S.-Africa summit, President Barack Obama said Friday, voicing confidence appropriate measures have been taken.

"Folks that are coming from these countries that have even a marginal risk, or an infinitesimal risk of having been exposed in some fashion, we're making sure we're doing screening on that end as they leave the country," Obama told reporters, adding there would be "additional screening" when they were in the U.S.

A federal judge has ruled that a ban on citizens carrying handguns in public in the U.S. capital Washington DC is unconstitutional.

In a 19-page opinion, Judge Frederick Scullin on Saturday ruled that "there is no longer any basis on which this Court can conclude that the District of Columbia's total ban on the public carrying of ready-to-use handguns outside the home is constitutional under any level of scrutiny.