WASHINGTON (AP) — A U.S. Navy ship fired three warning shots in the direction of an Iranian boat that was approaching another American ship head-on in the North Arabian Gulf on Wednesday, U.S. officials said, in an escalation of encounters in the region this week.According to U.S. Navy Cmdr. Bill Urban, the Iranian boat came within 200 yards of the USS Tempest and ignored several bridge-to-bridge radio calls and warning flares.