Paul Pillar comments  on the increasing divergence of interests between the U.S. and Saudi Arabia:
In Yemen, the United States has allowed itself to become associated with a destructive and misguided Saudi military expedition, and thus also with the humanitarian tragedy that the operation has entailed. The main Saudi objective is to show who’s boss on the Arabian Peninsula, another objective not shared with the United States. Saudi Arabia’s operation has shown itself, more so than Iran, to be a destabilizing force intent on throwing its weight around in the neighborhood.
Pillar doesn’t mention it here, but in addition to all this the war has been a boon to Al Qaeda in the Arabian Peninsula, which has been able to make gains in both Mukalla and Aden over the last few months. Besides having nothing to do with advancing U.S. interests, the Saudi-led war has been directly harmful to U.S. interests there. Insofar as it has helped jihadist organizations, the war has made the U.S. and the region less secure, and it has come at the great expense of the people of Yemen.
Human Rights Watch released a report  on Saudi Arabia to coincide with King Salman’s visit to Washington this week. Among other things, the report described the Saudi-led blockade and its effects:
The coalition-imposed blockade also has had a severe impact on Yemen’s civilians. According to the UN, 21 million Yemenis – a staggering 80 percent of the population – needed assistance and half the population faced food insecurity by September. More than 15.2 million people lacked access to basic healthcare, and over 20 million lacked access to safe water. With commercial imports accounting for 90 percent of Yemen’s food and fuel supplies, the coalition-imposed blockade may amount to starvation of civilians as a method of warfare, a war crime [bold mine-DL].
After more than five months of depriving the civilian population of basic necessities and preventing their access to humanitarian aid, I don’t think this needs to be qualified by saying that this “may” be a war crime. It seems clear at this point that the blockade is a deliberate and sustained effort to inflict punishment on the civilian population in violation of international law. I have said this before, but it bears repeating that U.S. participation in this cruel and unnecessary campaign is indefensible and disgraceful.