WASHINGTON — The White House asserted Monday it is highly likely that Syrian President Bashar Assad’s regime, not the rebel opposition, was behind any chemical weapons use in Syria.
Responding to weekend airstrikes in Syria, the White House also reiterated its view that Israel has the right to protect itself against weapons that could threaten Israelis.
White House spokesman Jay Carney said there is evidence chemical weapons have been used in Syria. And on Sunday, a member of a UN panel investigating events in Syria said there were indications that rebel forces had used the nerve agent sarin.
Carney questioned that claim.
‘‘We are highly skeptical of suggestions that the opposition could have or did use chemical weapons,’’ he said. ‘‘We find it highly likely that any chemical weapon use that has taken place in Syria was done by the Assad regime. And that remains our position.’’
President Obama has said the use of chemical weapons by the regime is a ‘‘red line’’ but he needs more time to determine if Assad’s forces had used chemical weapons in the fight. Carney says the United States is still looking for conclusive evidence and there is no timetable for the investigation.
In Geneva, Carla Del Ponte, a member of a UN commission looking into alleged war crimes and other abuses in Syria, made the suggestion about rebels’ use of chemical weapons.
Del Ponte, a former war crimes prosecutor, told Swiss public broadcaster SRI in an interview broadcast Sunday night that the indications are based on interviews with victims, doctors, and field hospitals in neighboring countries.
The four-member panel’s investigators have ‘‘strong, concrete suspicions but not yet incontrovertible proof of the use of sarin gas, from the way the victims were treated,’’ Del Ponte said.
Syria remains one of the most high-profile issues confronting the administration.
Airstrikes over the weekend on alleged Hezbollah-bound weapons in Syria and the status of chemical weapons kept the country’s civil war at the forefront. Lebanon’s Hezbollah militia is an ally of Syria and foe of Israel.
Secretary of State John Kerry traveled to Moscow on Monday to discuss the situation in Syria with President Vladimir Putin.
The administration hopes to convince Russia and other countries of the need to remove Assad from power before the war becomes a full-scale regional conflict.
‘‘We have consistently, in our conversations with the Russians and others, pointed clearly to Assad’s behavior as proof that further support for the regime is not in the interest of the Syrian people or in the interest of the countries that have in the past supported Assad,’’ Carney said.
‘‘We have been clear in the past about our disappointment with Russia over their opposition to resolutions at the Security Council with regards to this matter. But this is an ongoing conversation,’’ he said.
The Israeli government has not formally confirmed that it carried out the airstrikes Friday and Sunday, and Carney referred specific questions about the strikes to Israel.
‘‘Israel certainly has the right to be concerned about the transfer of sophisticated weapons to Hezbollah,’’ Carney said. ‘‘And that has been a concern of Israel’s for a long time. The transfer of sophisticated weapons to terrorist organizations like Hezbollah is certainly a concern and a threat to Israel.’’