BEIRUT—United Nations weapons inspectors arrived at one of the sites of last week’s presumed chemical weapons attacks outside Damascus, spurning U.S. calls for the team to stop their mission as American officials said they are inching closer to a decision for a military strike.
U.N. Secretary-General Ban Ki-moon rebuffed the U.S. request to withdraw the inspectors and “stood firm on principle,” according to a person familiar with the matter, ordering his team to continue their work establishing whether chemical weapons or toxins were responsible for the estimated hundreds of deaths of Syrian civilians.
Earlier Monday, the U.N. chemical weapons team came under fire from unidentified snipers as they examined the site of the suspected attack at Mouadhamiya, a few miles southwest of Damascus. The team retreated but returned later in the afternoon. Mr. Ban said the team visited two hospitals, interviewed survivors and doctors, and collect samples.
At the same time, U.S. officials were reaching a definitive conclusion that chemical weapons had been used by the Syrian government in military assaults last Wednesday. “Our confidence is growing that this was in fact an episode involving the use of chemical weapons by the Syrian regime,” a senior U.S. official said, the strongest remarks to date on the use of the banned weapons.
Secretary of State John Kerry was due to deliver a statement on Syria’s crisis at 2 p.m. Eastern Time, the State Department said.
Although President Barack Obama remains undecided on military action, the U.S. request for the U.N. team to withdraw echoed its moves before it attacked Iraq in 2003, when it asked a U.N. inspection team in Baghdad to withdraw for its own safety as it prepared for military operations.
In Iraq, U.N. inspectors investigating American claims that the regime of former president Saddam Hussein possessed weapons of mass destruction were pulled out after being notified that the U.S. was about to invade. That invasion didn’t have the backing of the U.N. Security Council, which would likely see Syrian allies Russia and China veto any proposed strike against Damascus. The U.S. could instead seek a mandate from the North Atlantic Treaty Organization.
The American message to Mr. Ban as of Sunday was that the U.S. believed there wasn’t adequate security for the U.N. inspectors to visit the affected areas to conduct their mission, a senior official in Mr. Obama’s administration said. The administration also told the U.N. that the U.S. didn’t think the inspectors would be able to collect viable evidence due to the passage of time and damage from subsequent shelling, this person said.
The suspected chemical weapons attacks occurred Wednesday, but the Syrian government gave permission to the U.N. team to access one of the areas on Damascus’s outskirts only on Sunday.
The U.N. has held firm against the U.S., with one official saying evidence of a chemical attack would still exist. Chemical traces could be found in survivors and vegetation for months, chemical-weapons experts said. The U.N. team in Damascus was there to investigate a suspected chemical weapons attack conducted months earlier in northern Syria.
On Monday, after their the U.N. convoy took fire, international investigators replaced a badly damaged vehicle and returned to Mouadhamiya at about 2 p.m., staying for nearly three hours, activists at the site said. An online photo that activists said was of the vehicle showed two bullets shattering the bulletproof glass of the front windshield and passenger window.
“The Secretary-General has instructed his head of disarmament, Angela Kane, to complain to both the Syrian Government and opposition and to demand that there be no repeat of today’s shooting,” said Martin Nesirky, Mr. Ban’s spokesman, in an email message.
“We frankly do not much care who did the shooting,” he said. “We are outraged that anyone would shoot at our team. They had just left the government checkpoint but had not yet reached opposition-held territory.”
The investigators’ decision to return to the site spoke volumes about the U.N.’s determination, said the person familiar with the U.S. pressure to withdraw.
U.N. investigators could be seen at one field hospital wearing their signature bright blue helmets and bulletproof vests, hovering above patients being treated for exposure to the suspected chemical weapons, in video posted by activists.
“What was your location?” one U.N. inspector asked a gaunt-looking male patient seemingly in his 40s.
“I was in Al Rawda mosque,” the man replied.
“What did you feel?” the inspector probed.
“It was [about] a minute and then I passed out,” the patient replied, to which the translator added he had “convulsions upon his arrival.”
What U.N. investigators find will weigh on any decisions by Western and Arab governments to strike at Syrian regime targets in response to the chemical weapons claims.
U.S. President Barack Obama has frequently said that any use of chemical weapons by the Syrian regime would be a red line, but has in the past backed down from that posture in previous incidents where the weapons were thought to be used.
But the latest suspected attack, carried out Wednesday, appears to behardening Mr. Obama’s resolve. Military leaders from the U.S., U.K., France, Saudi Arabia and Turkey, among others, kicked off a meeting in Jordan on Sunday evening to discuss the Syria conflict and weigh military action.
The U.N. inspectors are mandated only to determine whether chemical weapons were used, and not who may have used them, U.N. officials said.
But Germany said Monday it was “very likely” that the suspicions that the Syria regime used chemical weapons were true. “The alleged widespread use of gas has broken a taboo,” government spokesman Steffen Seibert said. “It requires consequences and a very clear response is needed.”
The U.K. said it is “clear” that the Assad regime was behind last week’s attack.
On the possibility of a military strike this week, British Foreign Secretary William Hague said in an interview with British Broadcasting Corporation on Monday that he wouldn’t rule anything out but declined to elaborate or discuss what military options are being discussed.
Mr. Hague said he believed it would be possible for the international community to launch a response even without unity on the U.N. Security Council. “It is possible to take action based on great humanitarian need and humanitarian distress,” said Mr. Hague. But, he said, any response would be subject to legal advice and must be in accordance with international law.
Russia’s Foreign Ministry said Monday that Foreign Minister Sergei Lavrov had called his U.S. counterpart on Sunday to express “deep concern” about the possible readiness of U.S. forces to “intervene.”
“The Russian side calls for [Washington to] refrain from the threat of force on Damascus, to not fall for provocations and to try to help create normal conditions to give the U.N. chemical experts’ mission, which is already in the country, the possibility of conducting a thorough, objective and impartial investigation,” the ministry statement said.
Syrian President Bashar al-Assad remained defiant in an interview with Russian newspaper Izvestiya, saying that any use of chemical weapons would defy logic and would be “an insult to common sense” as the area is near pro-regime neighborhoods.
The Syrian president went on to warn the U.S. that since Vietnam, it has failed at every military engagement it has fought and Syria would be no different.
“Have they not learned that they have gained nothing from these wars but the destruction of the countries they fought, which has had a destabilizing effect on the Middle East and other parts of the world?” Mr. Assad was quoted as saying in the newspaper.
Mr. Assad said the government is fighting terrorist groups in Syria whose threat would spread beyond the country’s borders.
“Politically speaking, when terrorism strikes Syria, a key country in the region, it would have a direct impact on stability in the Middle East,” Mr. Assad said.
An official from the North Atlantic Treaty Organization said NATO allies were closely monitoring developments in Syria and the wider region and “will keep the situation under constant review, as appropriate.”
“It’s important that the U.N. team should have access to the area to investigate these horrific reports, as any confirmed use of chemical weapons would be completely unacceptable and a clear breach of international law,” the official said. The issue was one for the entire international community to address, the official said.
The European Union’s top diplomat, Catherine Ashton, said the situation in Syria must be solved through a political process. If the U.N. inspectors determine there was a chemical-weapons attack, they first have to report back to the U.N. Security Council, she said Monday in Tallinn at a joint news conference with Estonia’s foreign minister.
—Adam Entous in Washington, Mohammad Nour Alakraa in Beirut and Julian E. Barnes in Jakarta contributed to this article.