WASHINGTON - US newspaper giant Gannett on Monday raised its bid for rival Tribune Publishing to $864 million after its earlier offer was rejected as too low.

Gannett hiked its bid from last month's $815 million in an effort to combine its USA Today and affiliated newspapers with the Los Angeles Times, Chicago Tribune and other dailies owed by Tribune Publishing.

"Our increased offer demonstrates our commitment to engaging in serious and meaningful negotiations with the Tribune Board to reach a mutually agreeable transaction where Gannett acquires all of Tribune," said a statement from Gannett chairman John Jeffry Louis.

"It is evident from our discussions with Tribune shareholders that there is overwhelming support for the companies to engage immediately regarding our proposed transaction. By increasing our offer at this time, we are reaffirming Gannett's belief that this transaction would deliver significant value to both companies' stakeholders and that the time to act is now."

Tribune Publishing issued a statement acknowledging it received the offer amounting to $15 per share, adding that its board "will thoroughly review" the revised proposal.

The two newspaper groups have been in a war of words over the bid.

Tribune Publishing said on May 4 the Gannett offer "understates the company's true value and is not in the best interests of our shareholders," and several days later adopted a shareholder rights plan or "poison pill" which makes a takeover more difficult.

Gannett president and chief executive Robert Dickey said Monday the revised offer "provides Tribune shareholders with a significant premium of 99 percent and immediate, certain value."

He added that "by not engaging constructively with Gannett and continuing to pursue an unproven strategy... we believe Tribune is jeopardizing its shareholders' investment and disregarding their best interests."

Tribune Publishing group was spun off the larger Tribune Co. in 2014, and has been examining options such as the sale of the coveted Los Angeles daily.

But following the Gannett offer the group said it would seek to remain independent as it refines its digital strategy.

Gannett last year became the latest media conglomerate to break itself apart, splitting off its television operations into a new firm called Tegna.