By nearly every measure offered by the United Nations, the scale of the tragedy unfolding in Yemen is staggering: More than 20 million people need urgent humanitarian aid. At least 14 million lack basic health care or access to clean water. And more than 900,000 suffer from suspected cases of cholera, a disease that — under almost all circumstances — should be preventable and treatable.

And aid agencies say Saudi Arabia's blockade of most of the country's major ports of entry is only deepening the crisis. Implemented in retaliation for the Houthi rebels' attempted missile strike on an airport in Riyadh, the closures are leaving humanitarian access "choked off, threatening the lives of millions of vulnerable children and families."

"Together, we issue another urgent appeal for the coalition to permit entry of lifesaving supplies to Yemen in response to what is now the worst humanitarian crisis in the world," reads a joint statement Thursday from World Food Program Executive Director David Beasley, UNICEF Executive Director Anthony Lake and World Health Organization Director-General Tedros Ghebreyesus.

"The supplies, which include medicines, vaccines and food, are essential to staving off disease and starvation," they continued. "Without them, untold thousands of innocent victims, among them many children, will die."

For years, war has raged between the Yemen's internationally recognized government and the Houthi rebels who seized Yemen's capital along with the country's northwestern region. A Saudi-led coalition intervened in 2015 and has conducted a relentless airstrike campaign in the country to support the predominantly Sunni government and suppress the Houthis, who are backed by Iran.

Despite this air campaign, which has been supported by the U.S., the fight has ground to a bloody stalemate in which neither side seems to gain or lose ground — even as the Yemeni civilians caught between them continue to lose much-needed infrastructure, medical facilities and often even their lives.

No portion of the population has been hit harder than Yemeni children. An estimated 130 children or more die per day in the country, according to Save the Children, which also has called on Saudi Arabia to lift the blockade.

"Even before this latest blockade, based on this calculation Yemen would expect to see about 50,000 malnourished children under the age of five die from hunger or disease this year," the group said Wednesday, adding that this amounts to roughly one child dying in Yemen every 10 minutes.

On Monday, Saudi Arabia's state-run media agency celebrated its delivery of food baskets to needy families and, as The Guardian reports, announced it would allow shipments of aid through several ports held by the Yemeni government. Other ports — such as rebel-held Hodeidah, the entry point for 80 percent of delivered aid, according to The Guardian — remain closed, however.

Saudi Arabia asserts it's necessary for these ports to be closed to prevent the transmission of weapons to rebels in the country.

But "even with a partial lifting of the blockade, the World Food Programme estimates that an additional 3.2 million people will be pushed into hunger. If left untreated, 150,000 malnourished children could die within the coming months," the three major aid agencies said in their statement Thursday, significantly adding to the figure presented by Save the Children.

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