Karen Mills, who served as Obama's administrator for small businesses, told CNBC that the tech giants would probably push to disrupt the market and deal a blow to established lenders.
"I think they are going to dominate the market, and that is the next phase that's coming," she told the LendIt Europe fintech conference in London.
"But the question is, in what form would that come, and... under what regulatory authority?"
Earlier this year, Amazon said it had lent more than $1 billion in small business loans to merchants looking to expand their businesses, via its website.
Online business loans have increasingly become the priority of a number of financial technology (fintech) lenders. U.S. digital lender Lending Club, for instance, allows investors to loan money directly to small and medium-sized enterprises (SMEs).
"When I look at it from a U.S. view and a global view, the banks are going to come back in full force, including Barclays and others, and then on top of that you're going to have definite presence of Amazon players," Mills told CNBC in an interview after the conference.