U.N. Secretary General Ban Ki-moon and his top Syria mediator sharply but indirectly criticized potential U.S. military strikes against Syria, saying any additional use of force could exacerbate the country’s civil war while violating international law.

Speaking on the margins of the Group of 20 summit in St. Petersburg, Ban delivered a stern warning about the risk of military action to a gathering of international dignitaries that was hosted by British Prime Minister David Cameron.

“I must warn that ill-considered military action could cause serious and tragic consequences, and with an increased threat of further sectarian violence,” he said.

Ban and his advisers have expressed growing unease about the risk that U.S. military action will inflame a Syrian crisis that has cost more than 100,000 lives and upend whatever slim hopes remain of forging a diplomatic solution.

Ban traveled this week to Russia with Lakhdar Brahimi, his special envoy on Syria, to try to revive a dormant U.S.-Russian initiative to organize political talks in Geneva between the Syrian government and the opposition.


How the intelligence stacks up

After a meeting with Russian Foreign Minister Sergei Lavrov, Brahimi said the prospects for holding such a meeting have been imperiled by the alleged Aug. 21 chemical weapons attack in the eastern suburbs of Damascus and “what may follow as a result of that.”

Like Ban, Brahimi stopped short of directly criticizing the United States. But he made it clear that any U.S. plans to use force against Syria without a U.N. Security Council mandate would be illegal.

“Syria is in very, very serious trouble, and we have been asked from time to time, ‘What about use of force by members of the international community?’ ” Brahimi told reporters. “We say what international law says. And international law says that no country is allowed to take the law into their hands; they have to go to the Security Council.”

A U.N. team is working around the clock to determine whether environmental and biomedical evidence, including soil, blood and urine samples collected at the site of the alleged attack, prove the presence of toxic agents.

Ten U.S. allies — Australia, Britain, Canada, France, Italy, Japan, South Korea, Saudi Arabia, Spain and Turkey — joined the United States in calling for action against Syria.

“We call for a strong international response to this grave violation of the world’s rules and conscience that will send a clear message that this kind of atrocity can never be repeated,” a statement issued by the group said. “The world cannot wait for endless failed processes that can only lead to increased suffering in Syria and regional instability.”

At a news conference in St. Petersburg, President Obama said that many of his foreign counterparts, with the exception of Russian President Vladimir Putin, share his view “that given Security Council paralysis on this issue, if we are serious about upholding a ban on chemical weapons use, then an international response is required, and that will not come through Security Council action.”