By AnnaMaria Andriotis, Brent Kendall and Peter Rudegeair

Visa Inc.'s $5.3 billion deal to buy a key player in the financial-technology space is in jeopardy because of antitrust concerns, according to people familiar with the matter.

The Justice Department could decide soon whether it will sue to block Visa's acquisition of Plaid Inc., a firm that provides the technological infrastructure underpinning an array of next-generation financial apps. After spending the better part of the year scrutinizing the deal, the department is concerned it could limit nascent competition in the payments sector, people familiar with the matter said.

The Justice Department has been making preparations for potential litigation, including lining up potential witnesses for a trial, some of the people said. No final decision has been made.

Spokespeople for Visa, Plaid and the Justice Department declined to comment.

Write to AnnaMaria Andriotis at annamaria.andriotis@wsj.com, Brent Kendall at brent.kendall@wsj.com and Peter Rudegeair at Peter.Rudegeair@wsj.com

(END) Dow Jones Newswires

10-27-20 1331ET