The White House said Tehran was providing weapons and tactical information to the Yemeni rebel group.
The US accused Iran of being “heavily involved in Houthi rebel attacks on merchant ships in the Red Sea.”
Tehran's support for the Yemeni rebel group includes both weapons and tactical intelligence, the White House said on Friday as it presented newly declassified intelligence that purportedly shows Iranian involvement in the attacks.
“We know that Iran was instrumental in planning operations against merchant vessels in the Red Sea,” White House national security spokeswoman Adrienne Watson said in a statement.
“This is consistent with Iran’s long-term material support and encouragement for the Houthis’ destabilizing actions in the region.”
“This is an international challenge that requires collective action,” Watson said.
The White House said visual analysis revealed nearly identical characteristics between Iran's KAS-04 drones and the unmanned vehicles used by the Houthis, as well as consistent characteristics between Iranian and Houthi missiles.
Al Jazeera could not independently verify the White House's claims.
The Houthis, who control swathes of Yemen including the capital Sanaa, have launched dozens of drone and missile attacks on merchant ships in the Red Sea, in what the group said was a show of support for Palestinians facing Israeli bombardment in Gaza.
The attacks effectively rerouted much of global trade by forcing cargo companies to sail around Africa, leading to higher costs and delays in the delivery of energy, food and consumer goods.
More than a dozen shipping companies, including Italian-Swiss giant Mediterranean Shipping Company, France's CMA CGM and Denmark's AP Moller-Maersk, have suspended transit through the Red Sea due to the attacks.
Washington announced earlier this week the launch of a multinational force involving more than 20 countries to protect ships transiting the Red Sea.
Last week, an American guided-missile destroyer shot down 14 attack drones believed to have been launched from Houthi-controlled regions in Yemen.
The Houthi leadership has warned that it will retaliate if it attacks “American battleships” and “American interests.”
Tehran has said it supports the Houthis politically but denies sending weapons to the group.
Iran's Foreign Ministry last month rejected Israeli allegations that the Houthis were acting under its leadership when they seized an Israeli-owned ship and denied responsibility for a drone shot down by a U.S. guided-missile destroyer.
The Houthis, who have effectively maintained a United Nations-brokered ceasefire with the Saudi-backed government since last year, revolted against the Yemeni government in 2014, sparking a devastating civil war.