"I think Iran’s support to Houthis, especially in areas like sending advanced weapons, is continuing without any diminution," the official said during a press briefing on Tuesday. "They might even be stepping it up."
According to the official, Iran’s support enables the Houthis to "threaten" Saudi Arabia to launch advanced missiles at civilian airports and, "potentially," threaten US citizens.
The official went on to say that international donors will suspend many assistance programs in Yemen over the next two months if Houthi rebels do not stop impeding aid operations.
The United States hopes that Houthi rebels will "change their behavior" and the measures to limit aid will not be necessary, the state department official added.
Earlier in February, the United Nations said it could reduce the humanitarian assistance to the northern Yemeni areas over the new restrictions imposed in the Houthi-controlled areas. Similar statements have been made by the United Kingdom and the United States.
Yemen has been engulfed in an armed conflict between government forces led by President Abdrabuh Mansour Hadi and the Houthi rebels since 2015, with Iran said to be providing support for the latter.
Iranian officials have repeatedly denied supporting Houthi attacks on Saudi Arabia.