The offer from Anbang, along with J. C. Flowers & Company and Primavera Capital, would represent the biggest Chinese takeover of an American entity, according to Dealogic. The Starwood board said in the statement that the binding and fully financed proposal “provides a high degree of closing certainty.”

Until this week, the deal between Starwood and Marriott was nearly complete. The companies agreed in November to combine after a competitive process also said to involve Hyatt Hotels Corporation. Shareholders were disappointed when the deal was announced, sending Starwood’s stock lower — the opposite of what typically happens to a seller’s stock. Since then, Marriott’s offer was weakened by a decline in the acquirer’s shares.

Cash represented an unusually small proportion of Marriott’s original offer. Marriott will need to increase the cash component as well as the overall value of the offer to prevail over Anbang, said Anthony Sabino, a professor of business law at St. John’s University.

“If Starwood’s shareholders agree with their board, then they will be bought out completely,” Mr. Sabino said. “They won’t care about what is inarguably Marriott’s stellar record of hotel operations, because they will just be pocketing the cash and moving on to other things.”

Anbang’s desire for Starwood appears to coincide with its interest in acquiring Strategic Hotels from the Blackstone Group for $6.5 billion. Strategic Hotels owns high-end hotels throughout the United States, such as the Four Seasons in Scottsdale, Ariz., and the JW Marriott Essex House hotel in Manhattan. Two years ago, Anbang agreed to acquire the Waldorf Astoria for $1.95 billion.