In famine-stricken Sudan, soup kitchens that feed hundreds of thousands of civilians trapped in a war zone have shut down.

In Thailand, war refugees with life-threatening diseases have been turned away by hospitals and carted off on makeshift stretchers.

In Ukraine, residents on the frontline of the war with Russia may be going without firewood in the middle of winter.

Some of the world’s most vulnerable populations are already feeling President Trump’s sudden cutoff of billions of dollars in American aid that helps fend off starvation, treats diseases and provides shelter for the displaced.

In a matter of days, Mr. Trump’s order to freeze nearly all U.S. foreign aid has intensified humanitarian crises and raised profound questions about America’s reliability and global standing.

“Everyone is freaking out,” Atif Mukhtar of the Emergency Response Rooms, a local volunteer group in the besieged Sudanese capital, Khartoum, said of the aid freeze.