This editorial appeared in the Washington Post.

It has been two weeks since Saudi Arabia imposed a land, sea and air blockade on Yemen, a country already devastated by two and a half years of Saudi bombing. Before the embargo, Yemen was suffering from the world's worst humanitarian crisis, according to the United Nations, with 7 million people on the brink of famine and another 900,000 stricken by cholera. Those conditions have now grown far worse — and yet the Saudis persist with their siege. It is time for the Trump administration, which has indulged the Saudi leadership for too long, to intervene.

Yemen's 28 million people depend on imports for up to 90 percent of their basic needs, including food, fuel and medicine. The vast majority of those imports come through the port of Hodeida, in northern Yemen, which along with the capital, Sanaa, is under the control of Houthi rebels. Saudi Arabia imposed the blockade after a missile allegedly fired by the Houthis came close to its capital, Riyadh. The Saudis blamed Iran for supplying the weapon.

U.N. humanitarian officials warned that the shutdown would quickly lead to an emergency. Now their predictions are coming true. According to the International Committee of the Red Cross, Sanaa, Hodeida and three other crowded cities — with 2.5 million people in all — have lost access to clean drinking water because of a lack of fuel.

One million children are at risk from an incipient diphtheria epidemic because vaccines are out of reach on U.N. ships offshore. According to Rasha Muhrez, Save the Children's director of operations in Yemen, several governates are down to a five-day supply of the fuel needed to operate flour mills, without which the millions dependent on food handouts will starve.

Three U.N. agencies — the World Health Organization, the World Food Program and UNICEF — issued a joint statement last Thursday saying that the continued shutdown "is making an already catastrophic situation far worse."

The Trump administration, through the State Department, has objected to the ongoing blockade and called for "unimpeded access" for humanitarian supplies. But many in Yemen suspect, with some reason, that the White House is tolerating, if not encouraging, the crime.

The White House has the leverage to put a stop to it. It should act immediately, or it will be complicit in a crime against humanity.