Express Scripts announced today that it is improving the cash portion of its offer for Caremark stock. The cash portion will accrue an additional 6% per annum beginning April 1.

Tomorrow is a big day in the Battle for Caremark as the Federal Trade Commission will announce whether it will undertake a second significant review of the Express Script proposal for anti-trust purposes. Medco CEO John Snow opined to Marketwatch that

If the FTC is favorable – meaning no second review or a minimal second review – I think Express has a very good opportunity here,” Snow told Marketwatch in an interview. But if the FTC has strong concerns about a merger between Medco’s wo biggest pharmaceutical benefits manager rivals, “…meaning there is a big risk factor associated with getting through the FTC process, then I think I’d tilt the scale to the CVS-Caremark merger,” Snow said.

The Wall Street Journal is reporting that the FTC is expected to give the Express Scripts / Caremark merger another look. Time is running out as the Caremark shareholders vote on the CVS merger proposal on March 16. Express Scripts lawyers also are hoping for an appellate victory in the Delaware courts that would stay that vote.