Tribune Publishing surges; Gannett not ready to drop bid, sources say

Shares of Tribune Publishing rose nearly 18 percent Monday after sources told CNBC that Gannett was not ready to drop its acquisition bid for the Chicago-based firm.

Gannett, the publisher of USA Today, made public an $815 million takeover bid for Tribune, which publishes the Los Angeles Times and the Chicago Tribune. Gannett's stock was up just 0.92 percent Monday.

Tribune said May 5 it has rejected Gannett's offer.

In an interview with CNBC's "Squawk Box," Tribune Chairman Michael Ferro said he thinks the company has assets that are "far more valuable than what [Gannet is] offering."

Tribune's shares have advanced more than 41 percent year to date and nearly 22 percent over the past six months.