DUBAI, United Arab Emirates — Yemen's Houthi rebels are enthusiastically "confronting America directly," the organization's leader said in a televised speech, vowing to continue the group's campaign of attacks on ships in the Red Sea until Israel's blockade of Gaza is lifted. The remarks came as the U.S. steps up its strikes on Houthi targets and ahead of President Joe Biden's admission to reporters that so far, his administration's military action was not having its intended effect. "When you say working, are they stopping the Houthis?" Biden said in an exchange with reporters in Washington, D.C. "No. Are they goi