While energy, climate change, the pandemic and conflict are the root causes of global food supply issues, the "most insidious source" is hunger used intentionally as a weapon of war, Ambassador Linda Thomas-Greenfield said.
"Regardless of how you feel about Russia, we all have a powerful common interest in mitigating the impact of the war in Ukraine on food security," she added.
French President Emmanuel Macron used similar language recently when he described the global food crisis as one of Russia's "weapons of war" during a visit to Cameroon.
Moscow denies responsibility for the food crisis and has blamed Western sanctions for slowing its food and fertilizer exports.
Thomas-Greenfield on Friday refuted that claim, instead suggesting that Russia had deliberately taken steps to disrupt global food supply chains while blaming the West.
African governments have largely avoided taking sides in the European conflict, and have refused to join Western condemnation and sanctions.
Africans "don't want to be pressured to pick a side" in a repeat of the Cold War, but "need to know the facts", Thomas-Greenfield said.
The United States has secured $4.5 billion for food security at the G7 summit, of which it has contributed $2.76 billion.
There are also plans for the U.S. to contribute $150 million in new humanitarian development assistance to Africa pending congressional approval, she added.