The CIA says the US has stopped sharing intelligence with Ukraine, less than a week after a bust-up between Donald Trump and Ukrainian President Volodymyr Zelenskyy.
The announcement came just two days after the Trump administration paused military aid to Ukraine.
So, what kind of intelligence had the two countries been sharing and how could this move affect the Russia-Ukraine war?
Here's what we know.
What did the US say?
US National Security Adviser Mike Waltz said the Trump administration had taken a "step back" and was "reviewing all aspects" of its intelligence relationship with Ukraine.
CIA director John Ratcliffe confirmed the move but said it was possible that both the military aid and intelligence sharing restrictions could "go away", saying the US would "work shoulder to shoulder with Ukraine".
Mr Waltz said the US was actively engaged in talks with Ukraine about moving negotiations forward on a minerals deal and a potential peace deal with Russia.
"I think we're going to see movement in very short order," he said.
What sort of intelligence had they been sharing?
The intelligence sharing between the US and Ukraine included people working directly with combat units, according to former CIA officer Glenn Carle.
"So, everything from down to the tactical level, up to the level of the president's office — strategic," he told the ABC's Radio National Breakfast program.
"It will consist of everything from human reports to assessments of plans and intentions and distributions of Russian forces, up to satellite imagery, which says the Russians have X number of tanks behind this hill or we expect that they're going to move a platoon here at a certain time."
Mr Carle said the suspension of intelligence sharing could have an instantaneous impact.
Washington had been sharing intelligence with Kyiv since Russia began its full-scale invasion of Ukraine in 2022.
To what extent has the intelligence been cut?
It is not immediately clear to what extent the US has cut back on its intelligence cooperation.
A source familiar with the situation, speaking to Reuters on condition of anonymity, said the Trump administration had halted "everything", including targeting data that Ukraine has used to strike Russian targets.
A second source said intelligence sharing had only "partially" been cut, but was unable to provide more detail.
What impact will this have on the battlefield?
Glenn Carle told Radio National Breakfast he believed the suspension would lead to more Ukrainians being killed.
"It will not only cost lives, but it's at the very least going to put the Ukrainians at more of a disadvantage than they were before," he said.
"It's absolutely consequential and a terrible development."
US intelligence assistance is vital for Ukraine to track Russian troop movements and select targets, the Associated Press reported.
Ukrainians use the information when operating US-supplied High Mobility Artillery Rocket Systems (HIMARS) and the US Army Tactical Missile System (ATACMS).
Intelligence from the US and other allies has also helped Ukraine prepare for Russian attacks, and supplied critical information in the war's early days that allowed Ukraine to thwart Russian President Vladimir Putin's hopes for a quick victory.
What happens next?
Comments from top Trump administration officials suggest the decision is part of the broader negotiations between Mr Trump and Mr Zelenskyy to negotiate a peace deal with Russia, and that intelligence could begin flowing to Ukraine again soon.
Addressing the US Congress on Tuesday (US time) Mr Trump said he was still in touch with Mr Zelenskyy in the wake of their televised falling out.
But Mr Carle says the move will only weaken Ukraine's hand in any negotiations.
"You have carrots and sticks in a negotiation," he said.
"And one of the sticks is the effectiveness of allied intelligence support to the Ukrainian military. If you just give that up, then the Russians will say, 'Well, thank you very much.'"
ABC/wires
