The giant Walgreens-Ride Aid merger could be in trouble, and their stocks plunged

It looks like the massive Walgreens-Rite Aid merger might be in trouble, just one week before the deadline to complete the deal.

US antitrust regulators "aren't sold" on the proposal, according to Bloomberg's David McLaughlin, Robert Langreth and Sara Forden.

The Federal Trade Commission may not finish its review before the deadline of January 27, according to the Bloomberg report. If that happens, Walgreens will pay Rite Aid a termination fee.

Walgreens has already pushed the deadline back from October 27 due to regulatory concerns. The deal was announced in October 2015 and valued at $17.2 billion.

Separately, a report from the New York Post last October said the supermarket chain Kroger may no longer be interested in acquiring 650 stores from the two companies as part of that deal.

Rite Aid's stock dropped as much as 18% on the news, while Walgreen's dropped 2.6%.