“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.”
In addition, he said, U.S. intelligence knows that the rockets containing the poison gas were launched “only from regime-controlled areas and went only to opposition-controlled or contested neighborhoods.”
The attack killed at least 1,429 Syrians, including at least 426 children, Kerry said.
Citing “many disturbing details about the aftermath” that are now known to U.S. intelligence, Kerry 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.”
An intelligence assessment released by the White House as Kerry spoke said the government has “high confidence that the Syrian government carried out the attack” and that the regime used “a nerve agent.”
The four-page document said those conclusions were drawn from “all-source” intelligence, including human, signals and geospatial sources, as well as a “significant body of open-source intelligence” such as videos and photographs posted on the Internet.
The conclusion, it said, was “the strongest position that the U.S. Intelligence Community can take short of confirmation.”
U.S. intelligence, it said, tracked preparation of the chemicals and their launch into the eastern Damascus neighborhoods. It said intercepted communications of senior Assad officials confirmed the weapons were launched and expressed concern about evidence that might be found by United Nations inspectors.
“After a decade of conflict, the American people are tired of war,” Kerry said. “Believe me, I am, too. But fatigue does not absolve us of our responsibility.” He said that “history would judge us all extraordinarily harshly if we turned a blind eye to a dictator’s wanton use of weapons of mass destruction against all warnings.”
Kerry spoke after French President Francois Hollande said Friday that his country is prepared to act in Syria despite Britain’s surprise rejection of military action, potentially making a nation that turned its back on Washington during the war in Iraq the primary U.S. ally in a possible strike against Syrian forces.
President Obama is weighing military action against Syria as a way of sending a strong message of disapproval to Assad, whom U.S. officials say is culpable for the apparent Aug. 21 chemical weapons attacks that killed hundreds of men, women and children in rebel strongholds on the outskirts of Damascus.
A U.N. team of chemical weapons experts has been gathering evidence at the sites of the alleged strikes this week and will present its findings Saturday to U.N. Secretary General Ban Ki-moon. The United States says it has clear proof that Assad’s government was involved in the attacks.
Although U.S. officials have said repeatedly that they are trying to assemble an international coalition to support military action, the administration also insisted Thursday that, if necessary, Obama has both the authority and the will to act on his own.
“There are few countries that have the capacity to inflict a sanction by the appropriate means. France is one of them,” Hollande said, according to the Reuters news agency. “We are ready. We will decide our position in close liaison with our allies.”
German Foreign Minister Guido Westerwelle told the Neue Osnabrücker newspaper that Berlin’s participation in a U.S.-led coalition has “neither been asked nor is it being considered by us.”
The American public opposes broad military action in Syria, according to an NBC poll released Friday, but is more open to limited weapons strikes that could undermine Syria’s chemical weapons capability. Still, an overwhelming majority of Americans want Obama to win the approval of Congress before authorizing such strikes, the poll found.
The possibility of American action in Syria has stirred concern among many current and former U.S. military officials, who say the mission seems ambiguous and the military is fatigued and overextended from the Iraq and Afghan wars.
The White House briefed key congressional leaders over the telephone for 90 minutes Thursday night, presenting what Rep. Eliot L. Engel (D-N.Y.) described as a strong argument that Assad’s government bore responsibility for poisoning hundreds of its citizens.
The evidence cited by administration officials included patterns of movement of Syrian officials around the time of the incident, and electronic intercepts of conversations of “some high-level officials” in Syria, said Engel, the top Democrat on the House Foreign Affairs Committee.
I don’t know if you can ever be 100 percent sure of everything,” Engel said. “But they seemed pretty sure.”
The White House said administration officials would “continue to engage” with members of Congress as Obama weighed his next steps.
House minority leader Nancy Pelosi (D-Calif.) said such that communication is essential and added that the president must also explain his thinking to the American people before taking any action.
“It is clear that the American people are weary of war,” Pelosi said in a statement. “However, Assad gassing his own people is an issue of our national security, regional stability and global security. We must be clear that the United States rejects the use of chemical weapons by Assad or any other regime.”
On Thursday, British lawmakers stunningly rejected the option of military intervention in Syria, despite an impassioned plea for action by Prime Minister David Cameron.
The decision, analysts said, potentially marked a bellwether moment for a country that has long stood as the global deputy to Washington’s global sheriff.
On Friday, Cameron sought to pick up the pieces of what the local media portrayed as a humiliating political defeat, saying he would continue to argue for a “robust response” to the alleged chemical weapons attack.
“We will continue to take a case to the United Nations, we will continue to work in all the organizations we are members of — whether the E.U., or NATO, or the G-8 or the G-20 — to condemn what’s happened in Syria,” Cameron told reporters in London. “It’s important we uphold the international taboo on the use of chemical weapons.”
At the same time, the prime minister said, “the potential . . . involvement of the British military in any action, that won’t be happening.” He said Parliament’s vote against taking action reflected “the great skepticism of the British people about any involvement in the Middle East.”
In Paris, the head of the Western-backed Syrian opposition said the strikes being contemplated by the United States and France are a moral responsibility that could level the playing field in Syria’s bloody civil conflict, now in its third year.
“Strikes can paralyze a large part of the regime and raise morale” within the opposition, Ahmad al-Jarba said on France-Inter radio, the Associated Press reported.
Obama and other Western leaders have said military strikes would be an attempt to punish Assad and to send a message that chemical attacks are unacceptable. The goal would not be to shift momentum in the battle between Assad’s forces and rebel fighters.
Hollande’s apparent willingness to take action in Syria stems, analysts say, from a number of variables. France is the former colonial power in Syria. The country, in military missions in Mali and Libya in recent years, has been reasserting its military might.
In addition, because the country sat out the war in Iraq, French politicians are not carrying the same painful baggage as those in Britain, whose troops joined the U.S.-led invasion of Iraq based on false intelligence that dictator Saddam Hussein was stockpiling weapons of mass destruction.
“There is no feeling here that ‘we are at it again’ or that ‘our government is lying to us,’ ” said Dominique Moïsi, senior adviser at the French Institute for International Relations in Paris. “We are in a better position to have public opinion favoring intervention in Syria.”
Faiola reported from London. William Branigin and Anne Gearan in Washington contributed to this report.