US Special Envoy for Yemen Tim Lenderking said on Thursday that several challenges remain despite the huge progress in the peace process in Yemen.
Lenderking told reporters in an online briefing on his latest visit to the region that Iran is still supplying arms and drugs that help fuel the war.
"The Iranians have continued to smuggle weaponry and narcotics toward this conflict and we are very concerned.”
"Despite the fact that we welcomed an agreement between the Saudis and the Iranians, I remain concerned about Iran's role," he said.
He was referring to the Chinese-brokered accord reached in March.
He contended that Tehran has trained Houthi fighters and equipped them "to fight and attack Saudi Arabia."
The United States will not reopen its embassy in Sanaa until it is confident the war is over and a "very firm and irreversible" peace process is underway, Lenderking said.