A senior Houthi official has told the Associated Press that the group has assured the Trump administration it will not attack US vessels in the Red Sea, while warning other countries against joining Saudi Arabia in Yemen's revived civil war.

The statement came as the Houthis fired a ballistic missile at Saudi Arabia's capital over the weekend. Mohamed al-Bukhaiti, a member of the group's political bureau, said Washington had reached out after Houthi forces advanced along Yemen's western coast towards the Bab el-Mandeb Strait.

The assurance is narrow. Al-Bukhaiti told the AP that the group was not targeting the United States or other nations in the strait, with the exception of Saudi Arabia. That distinction leaves commercial shipping navigating a conflict in which the boundary between state pressure, maritime security and regional war can move quickly.

The Red Sea is now one theatre in a much wider diplomatic contest. Iran's foreign minister is due to stop in Qatar before travelling to the UN General Assembly, while Egyptian and Saudi officials are discussing the regional crisis and freedom of navigation.

The Houthi message may reduce one immediate risk for US vessels, but it does not resolve the threat to shipping or the underlying war. It instead describes a conflict in which the Houthis are trying to turn maritime access into political leverage while Saudi Arabia seeks to prevent their consolidation along the coast.