WASHINGTON - Iraq has made the first payment in a deal to buy 18 F-16 warplanes worth a total of about $3 billion, the US State Department said on Tuesday."These aircraft are going to help provide air sovereignty for Iraq and to protect its territory," State Department spokeswoman Victoria Nuland said."They also, as a significant military sale between us, are a symbol of the commitment that we've made to the Iraqi government to have a long-term strategic partnership between the United States and Iraq," Nuland said.