There are now 20 million people on the brink of starvation across four countries grappling with extreme food shortages and conflict. But as the world suffers one of its most severe humanitarian crises in decades, President Donald Trump is threatening to drastically reduce foreign aid as part of his administrations America first budget.

Trumps proposed cuts come at a time when aid organizations say that more funding is desperately needed to save millions from dying. United Nations officials declared the worlds first famine in six years in parts of South Sudan in February and now fear that Nigeria, Somalia and Yemen are edging toward similar preventable crises.

Without collective and coordinated global efforts, people [in these countries] will simply starve to death, U.N. humanitarian coordinator Stephen OBrien warned in March. Days later, Trump unveiled the blueprint for his 2018 budget, which seeks deep cuts to humanitarian initiatives abroad.

The defunding of some U.S. foreign aid programs is already underway. Last week, the Trump administration halted all grants to the U.N. Population Fund, an organization that provides reproductive health care in more than 150 countries.

As the president awaits congressional approval for his proposed 28 percent slash in funding for USAID , which already accounts for less than 1 percent of the federal budget, experts working in each of the four at-risk countries talked to The Huffington Post about what such cuts could mean for their regions at this time.

Many aid officials agree that an increase in aid is not a panacea to the many humanitarian challenges facing Yemen, Somalia, Nigeria and South Sudan, but that more funding is desperately needed to stop these crises from plunging even deeper.

Weve always depended on very generous support in the U.S., World Food Programme Regional Director Valerie Guarnieri told HuffPost at a U.N. media briefing Tuesday. Any reduction [to foreign aid] in the U.S. budget would impact on our ability to reach people who are in need and our ability to avert a catastrophe.