The US is debating what more it might do to help the Syrian opposition in its conflict with the government, John Kerry, US secretary of state, has said, amid reports of fresh sectarian killing in the eastern part of the country.
The US has weighed for months whether to give arms to the rebels, but the issue is now firmly on the table given the increased involvement of Hezbollah, the armed Lebanese Shia group, and Iran in backing Syrian President Bashar al-Assad on the battlefield.
The diplomatic developments came on a day reports emerged of a raid by a group of Syrian rebels on a predominantly Shia Muslim village in Deir Az-zor province that resulted in the deaths of about 60 people, including many pro-government fighters.
Syrian forces are also reported to be preparing for a major offensive on rebel-held parts of the northern city of Aleppo.
"We are focusing our efforts now doing all that we can to support the opposition as they work to change the balance on the ground," Kerry said at a joint news conference with William Hague, UK foreign secretary, in Washington DC on Wednesday.
The Obama administration is meeting this week on the issue of arming the Syrian rebels, a topic that Kerry said he discussed with Hague.
The meeting will come in advance of a Group of Eight summit in Northern Ireland next week, where leaders will discuss a coordinated response to end the Syrian conflict and how to bring the rival sides together at a peace conference.
For his part, Hague said Britain, the US and allies in Europe and the region - a group known as the London 11 that has met in Turkish and Jordanian cities - may need to step up their efforts to help the opposition.
In-depth coverage of escalating violence across Syria
"Secretary Kerry and I are in complete agreement about this, and I also don't have any new announcement that we're making today about this, but we are determined that we will address this issue together and do our utmost to create the conditions for a political solution in Syria," Hague said.
Kerry made that clear that a political solution was the preferred outcome of the US.
"And I think that there's a unanimity about the importance of trying to find a way to peace, and not a way to war. The Assad regime is making that very difficult," he said.
Against this backdrop, Reuters news agency reported quoting diplomats that Western officials would meet the commander of the main force fighting Assad's forces to discuss new aid.
The diplomats said the representatives would be meeting Salim Idriss, the Free Syrian Army commander, on Saturday in northern Turkey to discuss possible new aid.
"Idriss needs money, munitions and weapons to cement his leadership and win credibility among the fighters," one diplomat said.
Sectarian killings reported
Meanwhile, the Britain-based Syrian Observatory for Human Rights (SOHR) watchdog group said Sunni rebels seized the village of Hatla on Tuesday, adding that the Assad government had armed hundreds of Shias in the area to fight against the rebels, who control large areas in the east.
The attack was reportedly carried out by rebel fighters in retaliation of the retaking of Qusayr by government troops last week.
Assad belongs to the Alawite sect, a Shia offshoot.
A video posted online by rebels on Tuesday, entitled "The storming and cleansing of Hatla", showed dozens of fighters carrying black Islamist flags celebrating and firing guns in the streets of a small town as smoke curled above several buildings.
"We have raised the banner 'There is no God but God' above the houses of the apostate rejectionists, the Shias, and the holy warriors are celebrating," the voice of the cameraman says.
One fighter shouts in the video: "This is a Sunni area, it does not belong to other groups."
The SOHR said most of the dead were pro-Assad Shia fighters as Shia civilians had fled. It was not possible to independently verify the account.
The Syrian government called the killings a "massacre" and some opposition members expressed concern about the nature of the attack.
The US and other Western nations have been hesitant to arm the outgunned and outmanned rebels because of "Sunni extremists" among their ranks.
Jen Psaki, US state department spokesman, said on Wednesday the US was "appalled by reports that rebels have killed 60 Shia in Hatla village".
"The motivations and circumstances surrounding this massacre remain unclear, but the United States strongly condemns any and all attacks against civilians,'' Psaki said.
Also on Wednesday, trouble flared on Syria's borders, with Lebanese police saying that a Syrian helicopter fired rockets on Arsaal, a village in the country's east, wounding at least two people.
The Syrian army command admitted in a statement that a Syrian helicopter "targeted terrorists who tried to flee to Lebanon, killing several of them and wounding others, while the rest sought refuge in Arsaal".
Lebanese security sources also reported fierce clashes on Wednesday night, between Hezbollah fighters and the al-Qaeda-linked Syrian rebel group al-Nusra Front, in the mountains near the border in the eastern Bekaa valley.