BAGHDAD — American senators visiting Iraq warned the Baghdad government Wednesday that it risked damaging relations with the U.S. if it is allowing Iran to fly over its airspace to deliver weapons to Syria.

An Iraqi government spokesman responded by saying Iran has told Baghdad the flights to Syria are only delivering humanitarian aid. He said the onus is on the U.S. to offer up proof that Tehran is shipping weapons.

Senator Joe Lieberman, an Independent from Connecticut, said Iraq's failure to stop the flights could threaten the long-term relationship with the U.S. as well as aid Iraq could receive as part of a 2008 strategic pact between the two nations.