US believes Syrian regime used chemical weapons

The White House said Thursday that the U.S. believes "with some degree of varying confidence" the Syrian government has used chemical weapons — specifically the nerve agent sarin — against its own people.

A letter from the White House to members of Congress said the assessment was based on "physiological samples" but called for a United Nations probe to corroborate it and nail down when and how they were used.

"We are continuing to do further work to establish a definitive judgement as to whether or not the red line has been crossed and to inform our decision-making about what we'll do next," a White House official said.

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