The United States ruled out Wednesday any suggestion that talks with Iran over its nuclear program are signs of warming relations between two countries whose diplomatic ties collapsed 35 years ago.

Iran and the so-called P5+1 -- Britain, China, France, Russia, the United States and Germany -- are trying to strike a deal that would prevent Tehran from developing a nuclear bomb, a goal it denies having. In return, Iran is seeking an easing of punishing economic sanctions. 

The U.S. military's top officer, General Martin Dempsey, told lawmakers on Wednesday it was possible special operations forces could eventually be sent to Syria to back up American-trained rebels.

But officials said Dempsey's comment was addressing a "hypothetical" scenario for the moment as moderate opposition forces have not yet been trained.

The United States is pushing the U.N. Security Council to threaten tough measures against the Syrian regime over its alleged use of chlorine in attacks, according to a draft resolution circulated to members on Wednesday.

The text obtained by Agence France Presse states that the Security Council "decides in the event of future non-compliance... to impose measures under chapter 7" of the U.N. charter, which provides for sanctions and possibly military force.

Syrian rebels launched a fierce attack Wednesday on an intelligence headquarters in Aleppo, leaving at least 34 dead, days after the opposition rejected a U.N. ceasefire plan for the city.

At least 20 members of regime security forces and 14 rebels were killed in a powerful blast and attack targeting air force intelligence offices in the west of Aleppo, the Syrian Observatory for Human Rights.

The apparent disintegration of a key Syrian rebel group has dealt a major blow to U.S. efforts to build up a force of moderate fighters to take on the Islamic State group.

The Hazm movement was seen as a cornerstone of the train-and-equip program Washington hopes will bring thousands of non-extremist fighters to bear against IS in Syria.

Saudi Arabia has beheaded dozens of convicts, including foreign drug traffickers, since the start of the year in what Amnesty International calls an unprecedented pace of executions in the kingdom.

Those put to the sword have included five Pakistanis, an Indian, two Jordanians, two Syrians and a Yemeni, with few foreign governments willing to publicly appeal for clemency from the wealthy Gulf state.

A former Royal Marine has become the first Briton to be killed while fighting with Kurdish forces battling Islamic State jihadists in Syria, leaving his family "devastated" Wednesday.

Konstandinos Erik Scurfield, 25, died on Monday in a battle with IS militants, a source in the Kurdish People's Protection Units (YPG) told AFP.

France cast doubt Tuesday on whether a U.N. plan to freeze fighting in the Syrian city of Aleppo will materialize, and blamed the Damascus regime for the setback.

French Ambassador Francois Delattre, who chairs the United Nations Security Council this month, said U.N. peace envoy Staffan de Mistura still has the full support of the 15-member council despite his unsuccessful efforts.

A foreign fighter believed to be either British or Greek has been killed in Syria while battling the Islamic State group alongside Kurdish militia, a monitor said Tuesday.

The Syrian Observatory for Human Rights said the man died early Tuesday from wounds suffered in a battle with jihadists the day before in the northeastern province of Hasakeh.

Syrian President Bashar Assad accused his Turkish counterpart Recep Tayyip Erdogan of backing extremism as he met Tuesday with visiting Turkish opposition figures.

"Erdogan leads with a destructive policy that does not serve at all the interest of his people, by supporting takfiri (extremist Sunni) forces," state news agency SANA quoted Assad as saying.