Last week, Chubb proposed an acquisition of The Hartford for a reported $23.2 billion in cash and stock.

The transaction could be the biggest insurance deal since Aon's $30 billion acquisition of Willis Towers Watson last year and the largest in the property-casualty insurance sector since ACE bought Chubb and its branding for $28.5 billion in January 2016.

Chubb presented The Hartford with “a proposal for a combination of our two companies that we believe would be strategically and financially compelling for both sets of shareholders and other constituencies," according to a statement issued by Chubb on Thursday.

The proposal values The Hartford at $65 per share and represents a premium of 26% based on its unaffected 20-day volume weighted average share price of $51.70 as of March 10.

“We have not yet received a response to our proposal but are looking forward to constructive, private discussions in order to expeditiously consummate a fair transaction that benefits all of our respective stakeholders," the statement said. “No agreement has been reached, and there can be no assurance any transaction will result from these discussions, and even if a transaction is agreed upon, there can be no assurances as to its terms, structure or timing."

In recent years, the p-c insurance sector has been an active area for mergers and acquisitions. Allstate struck a deal last year to buy National General Holdings Corp. for $4 billion in the insurer's largest purchase on record. In February, Progressive agreed to acquire Indiana-based trucking industry insurer Protective Insurance Corp. in a $338 million cash deal.

Will Jones is IA editor-in-chief.