Plans for AXIS Capital Holdings Ltd. and PartnerRe to merge are getting even more complicated, as they affirm their plans to combine and a rival bidder shows no sign of giving up.

Both companies issued a joint statement rebuffing the unsolicited $6.4 billion cash offer European investment company EXOR issued for PartnerRe in mid-April. As well, AXIS said it would sweeten the pot for PartnerRe shareholders with a one-time cash dividend of $11.50 per share in connection with its offer, assuming their merger deal actually closes.

EXOR isn’t going away quietly, however, having issued a statement that reaffirmed its offer and slammed the PartnerRe/AXIS deal and its updated shareholder enticement.

“The revised terms are a clear admission that the original transaction with AXIS, which was the result of a flawed process, undervalued PartnerRe, as is the case with the revised transaction,” EXOR said in its statement. ”

AXIS Capital President and CEO Albert Benchimol said that both Bermuda-based entities are still moving ahead with their integration plans.

“AXIS Capital and PartnerRe have already made significant progress toward realizing our shared vision of a broadly diversified global specialty insurance and reinsurance company with the scale, capital and market presence to compete at the highest levels of our industry,” Benchimol said in prepared remarks. “Throughout this process, we have only grown more confident about the transformational opportunity provided by this merger of equals.”

PartnerRe Chairman Jean-Paul Montupet added, also in prepared remarks, “the strategic, operational and financial merits of a unified PartnerRe and AXIS are significant and will create substantial value for all shareholders.”

EXOR, in turn, argued its proposal is “financially superior, with no financing conditions, can be completed swiftly and will retain and build upon PartnerRe’s highly talented management and employees.”

AXIS and PartnerRe noted that beyond the $11.50 per share cash dividend for PartnerRe shareholders if the merger closes, the original merger deal remains in place. Plans call for PartnerRe shareholders to receive 2.18 common shares of the combined company for each PartnerRe common share they own. AXIS shareholders, will get one common share of the combined company for each AXIS share they own. Once both companies combine, PartnerRe shareholders will have 51.5 percent of the company, with AXIS shareholders getting the other 48.5 percent.

EXOR slammed the one time enticement payment offer to PartnerRe shareholders of $11.50 per share as misleading, considering PartnerRe shareholders would own close to 52 percent of the combined PartnerRe/AXIS, which would make the incremental value to the PartnerRe shareholders “less than half of the proposed dividend.”

What’s more, EXOR argued that the extra payment would slash PartnerRe’s capital by more than $550 million and limit its financial strength in a major way. EXOR noted that A.M. Best placed PartnerRe and AXIS under review with negative implications, adding its all-cash offer keeps PartnerRe’s financial strength together and gives its shareholders “full and superior value.”

EXOR said it is “determined to pursue” its offer and “is fully committed to achieving its rapid completion.”

Meanwhile, Fitch Ratings said it has taking no rating action on either PartnerRe or AXIS since PartnerRe rejected EXOR’s offer. When the PartnerRe/AXIS merger deal was first announced in late January, Fitch placed PartnerRe on Rating Watch Negative, reflecting uncertainty about some aspects of the deal, such as the expected post-merger loss of some key PartnerRe executives and employees. It placed AXIS on Rating Watch Positive.

Currently, Fitch puts PartnerRe’s insurer financial strength rating at AA-, and places AXIS’ IFS designation at A+.

Fitch said it would ultimately affirm PartnerRe’s current ratings if the AXIS deal closes as planned, because it sees the merger creating “operating scale advantages” that would be helpful in the increasingly competitive reinsurance environment.