WASHINGTON — U.S. Secretary of State John Kerry said Monday that the use of chemical weapons in attacks on civilians in Syria last week was undeniable and that the Obama administration would hold the Syrian government accountable for what he called a "moral obscenity" that had shocked the world's conscience.
In some of the most aggressive language used yet by the administration, Kerry accused the Syrian government of the "indiscriminate slaughter of civilians" and of cynical efforts to cover up its responsibility for what he called a "cowardly crime."
Kerry's remarks at the State Department reinforced the administration's toughening stance on the Syria conflict, which is now well into its third year, and indicated that the White House was moving closer to a military response in consultation with America's allies.
Although President Barack Obama had not made a final decision on military action, he was likely to order a limited military operation — cruise missiles launched from American destroyers in the Mediterranean Sea at military targets in Syria, for example — and not a sustained air campaign intended to topple Bashar Assad, the Syrian president, or to fundamentally alter the nature of the conflict on the ground, the New York Times reported, citing unnamed administration officials.
The United States was expected to make public a more formal determination of chemical weapons use today, with an announcement of Obama's response likely to follow quickly, the Associated Press reported, citing administration officials. The officials insisted on anonymity because they were not authorized to publicly discuss the internal deliberations.
In the coming days, officials said, the nation's intelligence agencies will disclose information to bolster their case that chemical weapons were used by Assad's forces. The information could include so-called signals intelligence — intercepted radio or telephone calls between Syrian military commanders.
Other signs of Western momentum toward a military response also took shape on Monday. Britain's prime minister, David Cameron, cut short a holiday to deal with Syria, and the foreign ministers of Britain and Turkey suggested that bypassing the U.N. Security Council was an option. France's foreign minister, Laurent Fabius, said inaction was unacceptable.
"The only option I do not envisage is to do nothing," Fabius told Europe 1, a French radio station. France has been a close ally of the rebels seeking Assad's ouster in the country's civil war.
News media in Cyprus, where Britain maintains a military air base that is less than 100 miles from Syria's coast, reported stepped-up flights there in recent days, although such activity may not have been unusual.
Kerry spoke hours after U.N. inspectors were finally allowed access to one of the attack sites, despite shooting from unidentified snipers that disabled their convoy's lead vehicle. The inspectors still managed to visit two hospitals, interview witnesses and doctors and collect patient samples for the first time since the attack last week that claimed hundreds of lives.
Secretary General Ban Ki Moon said in a statement that he had instructed his top disarmament official, Angela Kane, who was visiting Damascus, to register a "strong complaint to the Syrian government and authorities of opposition forces" to ensure the safety of the inspectors after the assault. There was no indication that any member of the inspection team had been hurt.
Ban's spokesman, Farhan Haq, told reporters at a regular daily briefing at U.N. headquarters in New York that the assailants, who had not been identified, fired on the first vehicle in the convoy, which was "hit in its tires and its front window."
The visit by the U.N. inspectors to the Damascus suburb, in a half-dozen vehicles escorted by Syrian security forces, came shortly after Assad denied that his forces had used poison gas.
In an interview with the Russian newspaper Izvestia, published Monday, Assad said accusations that his forces had used chemical weapons were an "outrage against common sense" and warned the United States that military intervention in Syria would bring "failure just like in all the previous wars they waged, starting with Vietnam and up to the present day."
Obama administration officials said that Kerry's statement was calculated to rebut the claims made by Syria and its longtime patron, Russia, that the rebels were somehow responsible for the chemical weapons attack, or that Assad had made an important concession by giving the U.N. investigators access.
Kerry noted that on Thursday he had told Walid al-Moallem, the Syrian foreign minister, that if the Assad government had nothing to hide it should provide immediate access to the attack site.
"Instead, for five days, the Syrian regime refused to allow the U.N. investigators access to the site of the attack that would allegedly exonerate them," Kerry said. "Instead, it attacked the area further, shelling it and systematically destroying evidence."
He said: "The indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders by chemical weapons is a moral obscenity. By any standard, it is inexcusable. And despite the excuses and equivocations that some have manufactured, it is undeniable."
On Capitol Hill, top House and Senate Republicans called on the administration to confer with lawmakers before any military strike and to make the case to a skeptical public. The White House on Monday reached out to Speaker John Boehner after Boehner's office noted publicly that the speaker had not heard from the president on Syria.
"The speaker made clear that before any action is taken there must be meaningful consultation with members of Congress, as well as clearly defined objectives and a broader strategy to achieve stability," said Brendan Buck, a spokesman for Boehner.
Others welcomed the signals from the administration that it was preparing to take action. Sen. Bob Casey, D-Pa., said Assad "has crossed more than a red line and the United States must act in the interest of our national and global security."