(CNN) -- Turkey has temporarily closed crossings to and from Syria along its border due to fighting between opposition groups inside Syria, the Turkish Commerce and Customs Ministry said Wednesday.
The announcement came shortly after the United States and Britain suspended non-lethal aid to the Syrian opposition.
Syrian National Coalition spokesman Louay Safi called the move "a temporary measure to sort out the situation in northern Syria," where the Free Syrian Army lost a weapons depot to the Islamic Front in fighting in recent days.
The aid consisted of wood, medical items, non-military equipment like generators and communication equipment, he said. "I can't give you a particular date but I hope this can be solved," he added.
Several U.S. administration officials said Wednesday that the fate of Salim Idris, a top rebel commander supported by the West, was uncertain in the wake of the seizure of the warehouse.
U.S. officials said he had left Syria. They added that the seizure of the depot, a warehouse, could prove key in shaping how the United States deals with the Syrian opposition.
U.S. Ambassador to Syria Robert Ford is expected to travel this week to the region to meet with opposition members. The officials said U.S. authorities were considering expanding their contacts with moderate Islamists who are not affiliated with al Qaeda.
The Islamic Front, which announced its formation last month, is an alliance that includes tens of thousands of fighters from some of Syria's most powerful Islamist groups, including Ahrar al-Sham, Suqour al-Sham, the Islamic Army and the Tawhid Brigade. The groups control territory in key areas across Syria and have been fighting forces loyal to President Bashar al-Assad along the critical lines of Damascus and Aleppo, among other places.
The front's formation has diminished the stature of the Western-backed Free Syrian Army and its leadership abroad, the Syrian National Coalition, as leaders inside the country have sought to distance themselves from a command structure criticized for failing to serve the opposition's needs on the ground.
The alliance was formed after the al Qaeda-linked Islamic State of Iraq and the Levant -- known as ISIS -- succeeded as the predominant military force in northern Syria, marginalizing and even fighting Syria's more moderate factions.
ISIS's largely foreign fighting force poses a threat to rebel groups competing for funding, resources and influence in Syria.
The U.S. government suspended its aid Wednesday amid the instability near the Turkish border, State Department officials said. The suspension does not affect humanitarian aid efforts, they said.
The UK Foreign Office, in a statement, said it was "investigating events that took place over the weekend. While that investigation is under way, we will not be making any deliveries of equipment to the Supreme Military Council.
"We intend to resume support as soon as we and the SMC are satisfied the conditions on the ground allow the SMC to take safe delivery of equipment provided."
The blockage of passage to Turkey could have implications for refugees. The United Nations High Commissioner for Refugees reported in September that nearly 500,000 Syrians had registered or were awaiting registration as refugees in Turkey, and those numbers have been increasing since.
Meanwhile, a huge storm dubbed Alexa descended Tuesday and Wednesday on the region, dropping snow and rain whipped by high winds onto Turkey, Syria, Jordan and Lebanon, with the latter most affected, the UNHCR said.
In the Bekaa in eastern Lebanon, where thousands of Syrian refugees were living in tents, emergency crews were distributing aid, it said in a statement.
"Reports from Syria and parts of Turkey spoke of similarly grim conditions there," it said.
The Syrian conflict began in March 2011 after government forces cracked down on peaceful protesters during the Arab Spring movement and is now a full-blown civil war. The United Nations estimates that more than 100,000 people have died in the conflict.
CNN's Elise Labott, Salma Abdelaziz, Tom Watkins, Gul Tuysuz, Samira Said, Nick Paton Walsh, Saskya Vandoorne and Josh Levs contributed to this report.