<span style="color: #222222;">The United States yesterday urged complete cooperation with a probe into a Ukrainian flight's crash in Iran. According to media reports, Iran has rejected giving the Boeing plane's black boxes to Washington.</span><br />'' <br />'' <span style="color: #222222;">Without naming Iran directly, secretary of State Mike Pompeo said, the US calls for complete cooperation with any investigation into the cause of the crash.</span><br />'' <br />'' <span style="color: #222222;">The crash came as the tense relationship between Iran and the United States had sharply worsened, with Washington killing one of Iran's top generals. Hours before the crash Iran had fired missiles at bases in Iraq housing US troops</span><span style="font-weight: bold;">.</span><br />