WASHINGTON — Edging toward a retaliatory strike, the Obama administration today bluntly accused the Syrian government of Bashar Assad of launching a chemical weapons attack that killed at least 1,429 people — far more than previous estimates — including more than 400 children.

“Some cite the risk of doing things” in response, Secretary of State John Kerry said in a speech that acknowledged that Americans at home and U.S. allies abroad are weary of war. “But we need to ask what is the risk of doing nothing.”

Halfway around the world, U.N. personnel carried out a fourth day of inspection as they sought to determine precisely what happened in the attack last week.

The international contingent arranged to depart Syria on Saturday and head to laboratories in Europe with the samples they have collected.

President Barack Obama met with his national security aides at the White House as aides insisted he has not yet made a decision to attack military facilities belonging to the Syrian government.

Even so, the administration did nothing to discourage the predictions that he would — and soon.

“Our approach is to continue to find an international coalition that will act together,” said Defense Secretary Chuck Hagel, on a trip to the Philippines.