The Saudi-led military coalition fighting the armed Houthi movement in Yemen's civil war started a blockade of ports a month ago after Saudi Arabia intercepted a missile fired toward its capital Riyadh from Yemen.
Although the blockade later eased and showed signs of breaking on Wednesday, Yemen's situation remained dire. About 8 million people are on the brink of famine with outbreaks of cholera and diphtheria.
"I have directed officials in my administration to call the leadership of the Kingdom of Saudi Arabia to request that they completely allow food, fuel, water and medicine to reach the Yemeni people who desperately need it," Trump said in a statement, without elaborating.
"This must be done for humanitarian reasons immediately," Trump said.
The Norwegian Refugee Council (NRC) said the first food and fuel had arrived in Hodeidah and Saleef ports, but supplies were at a trickle compared to what was needed, since Yemen's population of 27 million was almost entirely reliant on imports for food, fuel and medicine.
Publicly, Trump, his top aides and senior Saudi officials have hailed what they say is a major improvement in U.S.-Saudi ties compared with relations under former President Barack Obama, who upset the Saudis by sealing a nuclear deal with their arch-foe Iran.
Even as ties improve, however, U.S. diplomats and intelligence analysts express anxiety over some of the more hawkish actions by Saudi Arabia's crown prince, especially toward Yemen and Lebanon, as Saudi Arabia seeks to contain Iranian influence.
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