(c) 2013, Bloomberg News.

(c) 2013, Bloomberg News.

WASHINGTON President Barack Obama said Friday the Syrian government's use of chemical weapons is a direct threat to U.S. and global security, and indicated the United States was ready to act to hold the Assad regime accountable.

"This kind of attack is a challenge to the world," Obama said in brief remarks at the White House.

He added that he hasn't made a final decision on his response, and that "in no event" will it involve U.S. troops on the ground in Syria. Any action will be "limited, narrow."

Obama spoke after his administration released a U.S. intelligence assessment that concluded with "high confidence" that the Syrian regime carried out a chemical attack that killed 1,429 people earlier this month in a Damascus suburb.

The report is a key part of the case being built by the Obama administration to justify taking military action against Syrian President Bashar Assad's government.

Obama referred to the inability of the U.S. and its allies to overcome objections to action by Russia and China at the United Nations Security Council and the surprise vote by the British House of Commons blocking Britain from taking military action.

France signaled it might act as the principal U.S. ally in a military strike against Syria, filling a hole left by Britain's unexpected desertion of the U.S.

"I recognize that all of us here in the United States, in Great Britain and many parts of the world, there's a certain weariness given Afghanistan. There's a certain suspicion of any military action post-Iraq," Obama said.

"Part of the challenge that we end up with here is that a lot of people think something should be done, but nobody wants to do it," he said.

Secretary of State John Kerry made a similar point earlier as he laid out the case made in the intelligence assessment.

If the U.S. doesn't respond, he said, "there will be no end to the test of our resolve and the dangers that will flow from those others who believe that they can do as they will."

The U.S. intelligence assessment concluded with "high confidence" that the Syrian regime carried out a chemical attack that killed 1,429 people earlier this month in an area near Damascus.

Three days before the Aug. 21 attack, U.S. intelligence officials concluded that personnel from the Syrian Scientific Studies and Research Center, a unit of Syria's Defense Department, were preparing chemical munitions, based on evidence including intercepted communications, satellite intelligence and spies.

The attacks began about 2:30 a.m. local time on Aug. 21, according to the report, and within four hours social media reported attacks from at least 12 locations.

Three hospitals in the Damascus region received about 3,600 patients with symptoms consistent with nerve-gas exposure.

According to the assessment, Syria maintains a stockpile of many chemical agents, including mustard, sarin and VX and has "thousands" of munitions to deliver them.

It said Assad is the ultimate decision-maker, who is surrounded by loyalists to carry out his wishes.

An administration official who briefed reporters on condition of anonymity declined to say whether the U.S. has concluded that Assad directly ordered the use of the chemical weapon.

The timing of the next move hangs in part on the work of a UN inspection team now in Syria that was mandated to determine whether a chemical attack occurred, not who ordered it and carried it out. The U.N. inspectors were scheduled to leave Syria by Saturday morning. Their departure would clear away an impediment for a strike to begin.

Obama also faces domestic hurdles. More than 100 of the 435 lawmakers in the House, including 18 of his fellow Democrats, signed a letter this week saying that Syria doesn't pose a direct threat to the U.S. and calling on Obama to seek congressional approval before taking any military action.

Obama said he will continue consulting with Congress without saying whether he will seek the approval from lawmakers.

Brendan Buck, spokesman for House Speaker John Boehner, said Obama still needs to lay out his objectives, strategy and legal justification for an attack.

"We the American people look forward to more answers from the White House," Buck said in a statement.

Almost 80 percent of Americans say Obama should seek congressional approval before taking any military action in Syria, according to a poll conducted Aug. 28-29 for NBC News.

Only 42 percent said they would support a U.S. military response, though that rises to 50 percent when the action specified is limited cruise-missile strikes targeted on infrastructure used to carry out chemical-weapons attacks.

The poll of 700 adults has an error margin of plus or minus 3.7 percentage points.

Obama also has his schedule to consider. He's set to leave the U.S. Sept. 3 for a trip to Sweden followed by attendance at the Group of 20 summit in St. Petersburg, Russia. The summit host is Russian President Vladimir Putin, who has been Assad's main ally.

While nothing would stop Obama from ordering a strike from overseas, it "would be unusual and awkward" for him to do so, said Damon Wilson, a former NATO and National Security Council official who's now executive vice president of the Atlantic Council, a policy group in Washington.

Also at the St. Petersburg summit will be British Prime Minister David Cameron and French President Francois Hollande, who said he still favors delivering a targeted blow against Syria.

"There are few countries with the capacity to mete out a sanction using appropriate means," Hollande said in an interview with the newspaper Le Monde published today. "France is among them and is ready."

_ With assistance from Michael C. Bender, Heidi Przybyla, Indira A.R. Lakshmanan, Nicole Gaouette and Gopal Ratnam in Washington, Sangwon Yoon in New York and Robert Hutton in London.