(c) 2013, Bloomberg News.

(c) 2013, Bloomberg News.

UNITED NATIONS The United Nations needs time to examine the "entire body of evidence" its inspectors collected on the alleged use of chemical weapons by Syria, Martin Nesirky, spokesman for the U.N. secretary-general, said.

The world body is "uniquely capable" of conducting an "impartial, credible" report, Nesirky told reporters Saturday in New York, after investigators completed a 14-day visit and left Syria.

A team of 13 U.N. scientists arrived in The Hague on Saturday after four days collecting evidence at a site outside Damascus that must be analyzed before they submit a report to Secretary- General Ban Ki-moon, Nesirky said. The U.N. won't provide a timetable for its final report, he said.

Secretary of State John Kerry said Friday that the U.S. already has clear evidence that Bashar Assad's regime used chemical weapons on Aug. 21 and wouldn't wait for the U.N. report to act against Syria.

On Saturday, President Barack Obama said he will seek authorization from Congress before taking planned military action, raising the possibility that the U.N. report will come out while Congress is debating the issue.

Ban on Friday told envoys of the five permanent members of the U.N. Security Council the U.S., U.K., France, Russia and China that the report may take as long as two weeks to prepare due to the required lab work, said two western diplomats who weren't authorized to comment and asked not to be identified.

The scientists will deliver the "biomedical and environmental" samples to two laboratories in Europe to establish a chain of custody for the evidence, Nesirky said Friday.

In Saturday's briefing, Nesirky called it "grotesque and also an affront" to view the departure of the chemical weapons inspectors as opening a "window for military action of some kind." More than 1,000 U.N. employees remain in Syria and will continue humanitarian aid work there, he added.

Because the U.S. has already established that chemical weapons were used, "the U.N. can't tell us anything that we haven't shared with you this afternoon or that we don't already know," Kerry told reporters Friday in presenting American intelligence findings that the weapons were used and Assad's regime was responsible.

Assad's regime has denied using chemical arms, and asked Ban on Aug. 28 to authorize an additional U.N. investigation into what it claims were three chemical weapons attacks by rebels against government soldiers.

Inspectors visited a government military hospital near Damascus Friday to evaluate information submitted by the Assad administration on the alleged attacks, according to Nesirky. He said Ban hasn't decided whether he will approve an additional probe.

Angela Kane, the U.N.'s disarmament chief, briefed Ban for an hour Saturday on the current status of the chemical-arms investigation, and they are doing "whatever can be done to speed up the process," Nesirky said.

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With assistance from Margaret Talev and Terry Atlas in Washington.

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