If the deal is blocked, the insurance giants would be better off just walking away from a merger agreement that was contentious from the start, analysts said.
"The way that it seems to me is that both Anthem and Cigna are realizing that there is no path to negotiations. There isn't going to be a negotiated settlement," said Ira Gorsky, an event-driven strategist who analyzes mergers at Elevation. "It's in their interest to break as quickly as possible and then get some sort of termination fee."
The two health insurers encountered skepticism from antitrust officials at their most recent meeting with the Department of Justice in late June, according to published reports. That meeting came weeks after contentious emails were made public, showing the two firms have been at loggerheads at times during the approval process.
An Anthem spokeswoman would not comment on the DOJ negotiations. In a statement to CNBC, she maintained that the two companies continue to work toward approval.
"Anthem and Cigna continue to be in ongoing dialogue with the Department of Justice and state regulators regarding the compelling combination of our two companies to increase consumer access to high quality, affordable healthcare," said Anthem spokeswoman Jill Becher.