U.S. Secretary of State John Kerry made clear on Friday that the United States would punish Syrian President Bashar al-Assad for the "brutal and flagrant" chemical weapons attack that it says killed more than 1,400 people in Damascus last week.
Kerry said it was essential not to let Syria get away with the attack, partly as a sign to those who might consider using chemical weapons in the future. He said the United States was joined by allies including France, "our oldest ally," in its determination to act.
"It matters here if nothing is done," Kerry said in a statement delivered at the State Department.
He said that if a "thug and a murderer like Bashar al-Assad can gas thousands of his own people with impunity," it would be an example to others, such as, he said, Iran, Hezbollah and North Korea.
"Will they remember that the Assad regime was stopped from those weapons' current or future use? Or will they remember that the world stood aside and created impunity?" Kerry said.
Kerry laid out a raft of evidence he said showed Assad's forces were behind the attack, and the U.S. government released an unclassified intelligence report at the same time including many of the details.
The report said the August 21 attack killed 1,429 Syrian civilians, including 426 children.
The intelligence gathered for the U.S. report included an intercepted communication by a senior official intimately familiar with the August 21 attack as well as other intelligence from people's accounts and intercepted messages, the four-page report said.
France said on Friday it still backed military action to punish Assad's government for the attack despite a British parliamentary vote against a military strike.
An aide to Russian President Vladimir Putin, a close Assad ally, seized on Thursday's British "no" vote which set back U.S.-led efforts to intervene against Assad, saying it reflected wider European worries about the dangers of a military response.
Assad's government has repeatedly denied carrying out the chemical weapons attack, blaming rebels who it suggested were trying to provoke intervention.
Syrian state television, which did not carry Kerry's speech live, reported that Kerry said the "first and last" aim of any action the Obama administration will carry out in the Middle East was to "guarantee the security of Israel".
Any military strike looks unlikely at least until U.N. weapons inspectors leave Syria on Saturday.
Kerry said their report would only confirm that chemical weapons were used, and he made clear that would not change much for Washington since "guaranteed Russian obstructionism" would make it impossible for the U.N. to galvanize world action.
"The primary question is really no longer, what do we know. The question is, what are we - we collectively - what are we in the world going to do about it," Kerry said.
He said the president had been clear that any action would be "limited and tailored" to punishing Assad, that it would not be intended to affect the civil war there and Washington remained committed to a diplomatic solution to the crisis.
The timing of any strikes may be complicated by Obama's departure late on Tuesday for Sweden and a G20 summit in Russia. He was not expected to order the strikes while in Sweden or Russia.
Kerry made clear Washington would not be swayed from acting either by the opinions of other states: "President Obama will ensure that the United States of America makes our own decisions on our own timelines, based on our values and our interests."
Kerry was speaking the day after British Prime Minister David Cameron failed to win parliamentary backing for military action in Syria.
Finance minister George Osborne, one of Cameron's closest allies, accepted that the vote had raised questions about Britain's future relations with its allies.
"There will be a national soul-searching about our role in the world and whether Britain wants to play a big part in upholding the international system," he said.
French President Francois Hollande told the daily Le Monde he still supported taking "firm" punitive action over an attack he said had caused "irreparable" harm to the Syrian people, adding that he would work closely with France's allies.
Hollande is not constrained by the need for parliamentary approval of any move to intervene in Syria and could act, if he chose, before lawmakers debate the issue on Wednesday.
"All the options are on the table. France wants action that is in proportion and firm against the Damascus regime," he said.
Britain has traditionally been the United States' most reliable military ally. However, the defeat of a the government motion authorizing a military response in principle underscored misgivings dating from how the country decided to join the U.S.-led invasion of Iraq in 2003.
Russia, Assad's most powerful diplomatic ally, opposes any military intervention in Syria, saying an attack would increase tension and undermine the chances of ending the civil war.
Putin's senior foreign policy adviser, Yuri Ushakov, said the British vote represented majority opinion in Europe.
"People are beginning to understand how dangerous such scenarios are," he told reporters. "Russia is actively working to avert a military scenario in Syria.
Even a limited strike risks causing unintended consequences.
Syrian ex-soldiers say that military sites in Syria are packed with soldiers who have been effectively imprisoned by their superiors due to doubts about their loyalty, making them possible casualties in any U.S.-led air strikes.
U.S. INTELLIGENCE REPORT
Kerry said the U.S. intelligence community had carefully reviewed and re-reviewed information regarding this attack. "I will tell you it has done so more than mindful of the Iraq experience. We will not repeat that moment."
Laying out the evidence, Kerry said Assad's government has the largest chemical weapons program in the Middle East and was determined to rid the Damascus suburbs of the opposition.
"We know that for three days before the attack, the Syrian regime's chemical weapons personnel were on the ground in the area, making preparations," Kerry said.
"And we know that the Syrian regime elements were told to prepare for the attack by putting on gas masks and taking precautions associated with chemical weapons."
He said rockets were launched from Assad-controlled areas and fell only on opposition-controlled areas, and he pointed to the thousands of reports and videos on social media from 11 sites in Damascus showing the impact of the attacks.
"We saw rows of dead lined up in burial shrouds, the white linen unstained by a single drop of blood," he said.
"We know that a senior regime official who knew about the attack confirmed that chemical weapons were used by the regime, reviewed the impact, and actually was afraid that they would be discovered," Kerry said.
"In all of these things that I have listed, in all of these things that we know - all of them - the American intelligence community has high confidence, high confidence. This is common sense. This is evidence. These are facts."
Some allies have warned that military action without U.N. Security Council authorization may make matters worse.
Russia holds veto power as a permanent U.N. Security Council member and has blocked three resolutions meant to press Assad to stop the violence since a revolt against him began in 2011.
Western diplomats say they are seeking a vote in the 15-member Council on a draft measure, which would authorize "all necessary force" in response to the alleged gas attack, to isolate Moscow and show that other nations back military action.
But China said there should be no rush to force a council decision on Syria until the U.N. inspectors complete their work.
"Before the investigation finds out what really happened, all parties should avoid prejudging the results, and certainly ought not to forcefully push for the Security Council to take action," Foreign Minister Wang Yi told U.N. Secretary-General Ban Ki-moon in a phone call, Xinhua reported.
The United Nations said its experts had completed the collection of samples and evidence from last week's attack.
U.N. spokesman Martin Nesirky said all the analysis of the samples must be completed before conclusions can be drawn and it was not clear how long that would take.
Elaborate bio-metric analysis of blood, hair or urine samples is expected to be done in laboratories in Sweden and Finland, which are among 22 used by the Organisation for the Prohibition of Chemical Weapons (OPCW) in 17 countries.
U.N. High Representative for Disarmament Affairs Angela Kane left Damascus on Friday via Beirut and was expected to stop in Istanbul before heading for New York.
Additional reporting by Matt Spetalnick, Andrea Shalal-Esa, Patricia Zengerle, Thomas Ferraro and Jeff Mason in Washington, Erika Solomon and Oliver Holmes in Beirut, Khaled Yacoub Oweis in Amman, Sarah Marsh in Berlin, Timothy Heritage in Moscow, Phil Stewart in Manila, Louis Charbonneau and Michelle Nichols at the United Nations, Lidia Kelly in Moscow, Ben Blanchard and Michael Martina in Beijing, John Irish in Paris and Andrew Osborn, Marie-Louise Gumuchian and Peter Apps in London; Writing by Alistair Lyon and Claudia Parsons; editing by David Storey