* Reports of use in north and in Damascus suburbs
* Obama warns of "red line" and consequences, but no details (Adds more quotes, background, comments.)
By Patricia Zengerle and Mark Hosenball
WASHINGTON, March 20 (Reuters) - The U.S. ambassador to Syria said on Wednesday there is no evidence so far to back reports that chemical weapons were used in Syria on Tuesday, but the United States has a large team investigating the issue.
"So far, we have no evidence to substantiate the reports that chemical weapons were used yesterday. But I want to underline that we are looking very carefully at these reports," Robert Ford, who was recalled from Damascus in February 2012, told a hearing of the House of Representatives Foreign Affairs Committee.
Separately, U.S. and European officials told Reuters there was no confirmation that either the forces of Syrian President Bashar al-Assad or his rebel opponents had used chemical weapons, as each side had asserted.
"We can't corroborate the CW claims at this point," one U.S. official said, speaking on condition of anonymity.
If confirmed, it would be the first use of such weapons in the two-year-old conflict.
Lawmakers also expressed concern about growing Iranian military support for Assad's government, and they pressed Ford on how the United States is pushing Baghdad over Iranian weapons pouring into Syria through Iraq.
"We have had very direct conversations with the Iraqis," Ford said, listing meetings in Washington and the Iraqi capital. "We have been very direct with them about the importance of not allowing Iran to exploit the crisis in Syria, and how that is not helpful to Iraqi interests, as well as the region's interests."
NO U.S. MILITARY AID FOR THE REBELS
Ford also said repeatedly in response to lawmakers' questions that the U.S. policy is not to provide military aid to the rebels.
Assad's government and rebels accused each other of launching a deadly chemical attack near the northern city of Aleppo on Tuesday. Both sides demanded international investigations. [
The White House and the State Department expressed deep skepticism over the Syrian government's claims regarding the rebels.
"We view this issue with extreme seriousness," Ford told the congressional hearing. "Right now we are trying to verify the reports we have seen recently about the use. There are reports about them being used both in the north and in the Damascus suburbs, the eastern suburbs of Damascus," he said.
U.S. President Barack Obama has warned that any use of chemical weapons would be a "red line" that would trigger consequences, without spelling out what those would be.
Ford said Washington has regular discussions with countries that have interests in Syria, urging them to "pass the warning" to Assad and his government. Syria has the largest stocks of chemical weapons of any country in the region, he said.
"The president has been very clear in saying that if Assad and those under his command make the mistake of using chemical weapons, or if they fail to meet their obligation to secure them, then there will be consequences and they will be held accountable," he said, declining to elaborate.
(Editing by Warren Strobel and Vicki Allen)