WASHINGTON (Reuters) - U.S. intelligence officials are looking into the possibility that chemical weapons may have been used in Syria in a limited form, although there is no consensus yet and additional analysis is required, a senior U.S. official said on Thursday.
"More review is needed," the senior U.S. official told Reuters, speaking on condition of anonymity.
The disclosure came as the U.S. Director of National Intelligence James Clapper said at a Senate hearing that the Syrian regime of President Bashar al-Assad "appears quite willing to use chemical weapons against its own people."
"We receive many claims of chemical warfare use in Syria each day and we take them all seriously, and we do all we can to investigate them," Clapper said.
Still, Clapper declined to say in the public hearing what the U.S. intelligence community had concluded about allegations of chemical weapons use by the Assad regime. He said keeping that assessment private was important "to protect the fragile, critical intelligence we need to assess the situation."
The concerns in the U.S. intelligence community add to a growing chorus of worry about chemical weapons in Syria. The government and rebels last month accused each other of launching a deadly chemical attack near the city of Aleppo.
Discussions between Syria and the United Nations on a U.N. investigation of allegations that chemical weapons were used in Syria have been at an impasse for over week due to the Syrian government's refusal to let the inspectors visit anywhere but Aleppo, diplomats and U.N. officials said.
Britain and France wrote letters to U.N. Secretary-General Ban Ki-moon last month urging him to ensure that inspectors also went to Homs, the site of another alleged chemical arms attack in December, and possibly Damascus.
U.N. diplomats said that Britain and France had provided Ban's office with what they believe to be strong evidence of chemical weapons use in Homs.
In what was the first visit by a U.N. secretary-general to the Pentagon, Ban discussed issues including the deteriorating situation Syria with U.S. Defense Secretary Chuck Hagel on Thursday, the Pentagon said.
Diplomats in New York say it is looking increasingly unlikely that the chemical inspectors will go into Syria, though they say that it will still be possible to investigate the allegations from outside the country.
The U.S. official who spoke to Reuters said that, even if there was use - something that there was no consensus about within the intelligence community yet - it appeared to be limited.
"We have no indication that, if chemical weapons were used, that it was a widespread event," the official said.
President Barack Obama has defined use of chemical weapons as a "red line" for the United States that would trigger unspecified U.S. action. But in recent days, senior U.S. officials testifying publicly before Congress have declined to say whether chemical weapons may have been used.
Clapper, asked whether Syria might have crossed that red line, declined to comment, saying drawing such a conclusion would ultimately be a policy matter.
Additional reporting by Louis Charbonneau in New York; Editing by Cynthia Osterman