"While there are numerous problematic actors inside of Yemen, the Houthis bear major responsibility for refusing to engage meaningfully on a ceasefire and to take steps to resolve a nearly seven-year conflict that has brought unimaginable suffering to the Yemeni people," the State Department said.
Since taking office in January, US President Joe Biden has made Yemen a priority and appointed Lenderking to help revive stalled UN peace efforts.
After Lenderking returned from a visit last month, the State Department accused the Houthis of worsening Yemen's humanitarian crisis by attacking Marib, the last northern stronghold of the Saudi-backed government that the Houthis drove out of the capital.
The situation has not changed.
"The Houthis continue a devastating offensive on Marib that is condemned by the international community and leaves the Houthis increasingly isolated," the State Department said.
Lenderking had talked to Yemenis about strengthening "inclusive processes" that could help citizens discuss the country's future and increase efforts towards peace, it said.