Other departments, as well as international development funding for poorer countries, would decrease in order to finance the US President's proposed defence budget increase of $54 billion (£43 billion) to $657 billion in total.
Michael Wear, who directed faith outreach for former President Barack Obama's successful re-election campaign in 2012, told Premier: "It's oxymoronic. It's just plain moronic.
"Cutting foreign assistance makes us less safe. Foreign aid is already a relatively small percentage of the American budget and we use those dollars extremely well."
Mr Trump is expected to reveal more details of his economic plans for next year's budget during his first address to a joint session of Congress on Wednesday evening.
Michael Wear went on to say: "The case that Christians are making in the country - and the case that I'm making - is that you don't put America first by putting American values last.
"We should be increasingly the foreign aid budget at a time of such global upheaval."
Boosting the United States' military was among the pledges made by Mr Trump during his campaign to become president.
After input from government agencies is received, a finalised version of his budget will be sent to Congress in mid-March, where it's expected to face fierce opposition.
Believing plans to boost the defence budget at the expensive of foreign aid could prompted a big battle among US politicians, Michael Wear added: "I think these fights are going to be tense.
"It will require Democrats building partnerships across the aisle [with Republicans] if we're going to protect the social safety net, if we're going to protect international aid dollars. It's possible."
Click here to listen to Premier's Alex Williams speaking with Michael Wear: