The FBI is investigating the hijacking of Newsweek's Twitter feed Tuesday by pro-Islamic hackers in which a threat was made to President Barack Obama's family, the White House said.

White House spokesman Josh Earnest told reporters that  "this particular intrusion is one that is already being investigated by the FBI," without elaborating.

U.S. President Barack Obama called his Russian counterpart Vladimir Putin to discuss escalating violence in eastern Ukraine and "Russia's ongoing support for the separatists there," the White House said Tuesday.

During the call Obama reiterated America's support for Ukraine's "sovereignty and territorial integrity," National Security Council officials said.

Five of the six world powers negotiating with Iran over its nuclear program have stepped back, leaving Washington to hammer out a deal with Tehran, a key U.S. lawmaker said Tuesday.

"It's evident that these negotiations are really not P5+1 negotiations any more," Senate Foreign Relations Committee Chairman Bob Corker said as he emerged from a closed-door briefing by Obama administration officials on the status of nuclear talks with Iran.

Damascus receives "information" about air strikes by the U.S.-led coalition against the Islamic State group in Syria, President Bashar Assad said in an interview published on Tuesday.

"Sometimes, they convey a message, a general message," he said in an interview with the BBC in Damascus.

Perturbed by Thailand's coup, the United States has scaled back a showpiece joint military exercise with its Southeast Asian ally, but analysts say that with China circling for influence, Washington will not push the kingdom's generals too far.

Famed for its jungle bonding sessions where U.S. and Thai soldiers down snake blood, the annual "Cobra Gold" event is the crown jewel of Thailand's decades-long strategic alliance with the U.S.

U.S. President Barack Obama on Monday agreed to hold off a controversial decision on sending arms to Ukraine until German-led efforts to broker a ceasefire with Russia are given a chance. 

Hosting Chancellor Angela Merkel at the White House, Obama said he hoped she could reach a deal with Russian President Vladimir Putin to end 10 months of bloodshed in eastern Ukraine, but warned more punitive measures are in the pipeline if that fails.

A military judge halted a hearing at Guantanamo after defendants accused of the September 11, 2001 attacks complained that the court interpreter had worked in the CIA's secret prisons.

Ramzi Binalshibh, one of the five accused, was the first to object to the interpreter's presence in the court room.

Israeli Prime Minister Benjamin Netanyahu said Monday he is determined to address Congress next month over Iran's nuclear program, brushing off U.S. fears his intervention could derail talks with Tehran.

"I am determined to address Congress, that is why I decided to go to Washington and present Israel's position," Netanyahu told participants at an election event by his Likud party.

U.S. President Barack Obama said Monday there was no reason to extend nuclear talks with Iran once again, stressing the question now is whether Tehran truly wants an agreement.

"I don't see a further extension being useful if they have not agreed to the basic formulation and the bottom line that the world requires to have confidence that they're not pursuing a nuclear weapon," Obama said at a joint press conference with visiting German Chancellor Angela Merkel.

Kurdish forces backed up by U.S.-led air strikes have recaptured territory from Islamic State jihadists near the strategic city of Mosul in northern Iraq, the American military said Monday.

The advance is the latest push by Kurdish forces around Mosul, considered a crucial battleground for an eventual major counteroffensive against the IS group by Iraqi government troops and the Kurds.