The Trump administration's decision to pause U.S. foreign aid would undo progress made in containing tuberculosis (TB) infections across low- and middle-income countries, putting the lives of millions at risk, the World Health Organization said on Wednesday.

"Without immediate action, hard-won progress in the fight against TB is at risk. Our collective response must be swift, strategic, and fully resourced to protect the most vulnerable and maintain momentum toward ending TB," said Tereza Kasaeva, director of WHO's Global Programme on TB and Lung Health.

Critical international aid, particularly from the U.S. Agency for International Development (USAID), helped avert about 3.65 million deaths last year alone from the deadly disease, according to the agency.

The U.S. has historically contributed about one quarter of the total international donor funding for TB programs, which amounts to about $200 million to $250 million annually in bilateral funding, the WHO said.

Additionally, the USAID has also halted all its funded trials, severely impeding progress in TB research.

The funding disruptions put 18 of the highest TB-burden countries at risk, with the African region being the most affected followed by the South-East Asian and Western Pacific regions. These regions depend on 89% of the expected U.S. funding for TB care, the agency said.

The funding withdrawals are already pulling apart essential services in these countries, including testing and monitoring systems, drug supply chains and thousands of health workers facing layoffs.

In a move that could ease concerns, the U.S. Supreme Court on Wednesday declined to let the Trump administration withhold payment to foreign aid organizations for services already rendered to the government.