The Biden administration is expanding efforts to surveil and intercept Iranian weapons being smuggled to Yemen, where Houthi militants have staged a deadly campaign of violence against commercial shipping that has proved resilient to six weeks of military strikes, said U.S. officials familiar with the matter.

The initiative seeks to map seafaring routes used by Tehran and stop the arms shipments while in transit, an acknowledgment that the Houthis are likely to pose a significant security challenge for the foreseeable future. 

It is part of a broader strategy that also includes sanctions and diplomatic pressure, but faces constraint as essential military resources are in short supply.