PARIS — France released an intelligence report on Monday alleging chemical weapons use by Syria’s regime that dovetailed with similar US claims, as President Bashar Assad warned that any military strike against his country would spark an uncontrollable regional war and spread ‘‘chaos and extremism.’’
The verbal crossfire, including a rejection of the Western allegations by longtime Syrian ally Russia, was part of frenzied efforts on both sides to court international public opinion after President Obama said he would seek authorization from Congress before launching any military action against Assad’s regime.
In an interview with French newspaper Le Figaro, Assad was quoted as saying that Syria has challenged the United States and France to provide proof to support their allegations, but that their leaders ‘‘have been incapable of doing that, including before their own peoples.’’
‘‘If the Americans, the French, or the British had a shred of proof, they would have shown it beginning on the first day,’’ he said, deriding Obama as ‘‘weak’’ and having buckled to US domestic political pressure.
‘‘We believe that a strong man is one who prevents war, not one who inflames it,’’ Assad said.
President Francois Hollande of France and Obama have been the two world leaders most vocally calling for action against Assad’s regime, accusing it of carrying out a deadly chemical attack against rebel-held suburbs of Damascus on Aug. 21.
The United States said it has proof that the Assad regime is behind attacks that Washington claims killed at least 1,429 people, including more than 400 children.
Those numbers are significantly higher than the death toll of 355 provided by the aid group Doctors Without Borders.
It has marked an intolerable escalation in a two-year civil war in Syria that has left some 100,000 people dead.
The Syrian government denies the allegations and blames opposition fighters.
In the Figaro interview, Assad questioned whether an attack took place at all and refused to say whether his forces have chemical weapons, as is widely believed.
If the United States and France strike, ‘‘Everyone will lose control of the situation. . . . Chaos and extremism will spread. The risk of a regional war exists,’’ he added.
To back up its case, the French government published a nine-page intelligence synopsis Monday that concluded Assad’s regime had launched an attack on Aug. 21 involving a ‘‘massive use of chemical agents,’’ and could carry out similar strikes in the future.
In all, though, the French report provided little new concrete evidence beyond what US officials provided over the weekend in Washington.