The United States has decided to limit military support to Saudi Arabia's campaign in Yemen because of concerns over widespread civilian casualties and will halt a planned arms sale to the kingdom, US officials say.
The United States will also revamp future training of the kingdom's air force to focus on improving Saudi targeting practices, a persistent source of concern for Washington.
The decision reflects deep frustration within US President Barack Obama's government over Saudi Arabia's practices in Yemen's 20-month-old war, which has killed more than 10,000 people and sparked humanitarian crises, including chronic food shortages, in the poorest country in the Middle East.
It could also further strain ties between Washington and Riyadh in the remaining days of Obama's administration and put the question of Saudi-US relations squarely before the incoming administration of US President-elect Donald Trump, who takes office on January 20.
A Saudi-led military coalition intervened in Yemen's civil war in March 2015 and has launched thousands of air strikes against the Iran-allied Houthi movement.
Rights groups say attacks on clinics, schools, markets and factories may amount to war crimes. Saudi Arabia has either denied the attacks or cited the presence of fighters in the targeted areas and has said it has tried to reduce civilian casualties.
An Obama administration official, who spoke on condition of anonymity, said "systemic, endemic" problems in Saudi Arabia's targeting drove the US decision to halt a future weapons sale involving precision-guided munitions.
"We've decided not to move forward with some foreign military sales cases for air-dropped munitions, PGMs (precision-guided munitions)," the official said.
"That's obviously a direct reflection of the concerns that we have about Saudi strikes that have resulted in civilian casualties," the official said. A second official confirmed the decision to suspend the sale of certain weaponry.
The White House launched a review of US assistance for the Saudi-led coalition after planes struck mourners at a funeral in the capital, Sanaa, in October, killing 140 people, according to one UN estimate.
The United Nations human rights office said in August that the Saudi-led coalition was responsible for roughly 60 percent of the 3800 civilians killed since March 2015.