ISTANBUL — Ending Syria’s civil war through negotiations became an even more remote prospect Monday, as the main opposition group prepared to set up a rival government to President Bashar Assad’s regime and the United States said it will not stop others from arming the rebels.
The opposition Syrian National Coalition met in Istanbul to elect a prime minister who would run an interim government in Syria’s rebel-held areas. They picked Ghassan Hitto, a Syrian-born computer systems manager from Texas, who received 35 votes out of 49 ballots cast early Tuesday. Hitto will select ministers in coming days.
In Washington, Secretary of State John F. Kerry said the Obama administration wants to leave the door open for a political solution in Syria but said it would not oppose a plan by Britain and France to arm the rebels directly.
‘‘The United States does not stand in the way of other countries that made a decision to provide arms, whether it’s France or Britain or others,’’ Kerry said.
Also on Monday, Assad’s fighter jets and helicopters struck targets near the town of Arsal, Lebanon, according to Lebanon’s state-run National News Agency. The two countries share a porous border.
State Department spokeswoman Victoria Nuland confirmed that Syrian aircraft fired rockets into northern Lebanon, striking near Arsal.
Syrian forces have occasionally fired guns or mortar rounds across the Lebanon border in clashes with anti-Assad fighters but had never before used warplanes to attack suspected rebel positions inside Lebanese territory. “These kinds of violations of sovereignty are absolutely unacceptable,’’ Nuland said.
Setting up an opposition government, in a direct challenge to the Syrian regime, could harden battle lines even more and close the door to negotiations between Assad and the opposition.
The United States has been cool to the idea of a rival government, saying the focus should be on a political transition. Under a plan endorsed by the international community last year, Assad’s supporters and opponents were to propose representatives for a transition government, with each side able to veto candidates.
But the plan did not address Assad’s role. Most in the Syrian opposition rule out any negotiations with the Syrian ruler.
Kerry’s comments on sending weapons to the rebels came after French President Francois Hollande said last week that his country and Britain were pushing the European Union to lift its arms embargo on Syria as soon as possible.
The two countries are seeking military help for the rebels by the end of May or earlier if possible. Germany and other EU nations have been skeptical, pointing to the risk of further escalation.
Britain and France maintain that Assad will not hold genuine negotiations if he believes he can survive militarily and that strengthening the rebels is the only way of squeezing the regime.
Kerry’s remarks indicate that the Obama administration will not interfere with any country seeking to rebalance the fight against an Assad regime supported by Russia, Iran, and Hezbollah.
The United States long argued that more weapons in Syria would only make peace harder. As the violence has worsened over the last year, Washington has tempered that message somewhat. It is now promising nonlethal aid to the anti-Assad militias in the form of meals and medical kits and refusing to rule out further escalation.
The Syria uprising erupted in March 2011 as a largely peaceful uprising. In response to a regime crackdown, the rebellion turned into an armed insurgency and then civil war. More than 70,000 people have been killed and some 4 million of Syria’s 22 million people have been driven from their homes, UN estimates say.