The company, based in Phoenix, assisted with military healthcare for 16 years. It has said it might not survive losing the Pentagon's business, according to reports.
Experts said they expect the dispute to continue.
"There’s an awful lot at stake for TriWest, so they may want to go down fighting and they may win," Sheryl Skolnick, an analyst with CRT Capital Group, told Bloomberg.
"Until the last possible avenue of protest is exhausted, I have a feeling this contract won’t be finally awarded.”
Tri-West recently retained a D.C. lobbying firm — Denny Miller Associates — according to public records.
—This post was updated at 5:31 p.m.