US Special Envoy for Yemen Tim Lenderking is travelling to Saudi Arabia and Oman on Thursday for talks with government officials about efforts to end the civil war and smooth the delivery of assistance to the world’s worst humanitarian disaster, the US State Department said. Mr Lenderking's meetings "will focus on ensuring the regular and unimpeded delivery of commodities and humanitarian assistance throughout Yemen, promoting a lasting ceasefire and transitioning the parties to a political process", the State Department said.<br/> The war started in 2015 when the Iran-aligned Houthi rebels took control of the capital, ousting the internationally recognised government. A Saudi Arabia-led military coalition intervened at the government's request. Yemen is currently suffering from the world’s worst humanitarian standards, according to the United Nations, with about 80 per cent of the country's population of 29 million requiring aid and 13 million facing starvation. Mr Lenderking's visit comes a day after Iran's Foreign Minister Javad Zarif met Houthi rebel spokesman Mohammed Abdul Al Houthi in Oman on Wednesday. In his meeting, Mr Zarif reiterated Tehran's support for a ceasefire and a return to talks to end the country's long conflict, the Iranian Foreign Ministry said. On Tuesday, Saudi Crown Prince Mohammed bin Salman called on the Houthis to stop fighting and start peace negotiations. The Houthi spokesman and other leaders of the rebel group live in exile in Muscat. Since taking office in January, US President Joe Biden has made Yemen a priority and he appointed Mr Lenderking as the first envoy to the country to help revive stalled UN efforts to end the conflict. Saudi Arabia proposed a comprehensive ceasefire and a return to the negotiating table, a proposal that the Houthis immediately rejected, saying a blockade on the country must first be lifted. De-escalation efforts come as the war in Yemen flared anew in the past two months with a rebel campaign to seize Marib city, the government's last stronghold in the north. Mr Lenderking "will build on the international consensus to halt the Houthi offensive on Marib, which only worsens the humanitarian crisis threatening the Yemeni people", the State Department said. Last week, Mr Lenderking called the battle for the Marib region the single biggest threat to peace efforts. He said Iran's support for the Houthi movement was "quite significant and it's lethal". Iran denies supporting the Houthis.