The fight for Starwood Hotels swung back in favor of China’s Anbang after the insurance company offered $15 billion in a counterpunch to Marriott International.

Starwood Hotels & Resorts Worldwide, which has a tony stable of hotels including the St. Regis New York, said Monday that the offer from the Anbang group is "reasonably likely" to trump a sweetened bid that Marriott submitted last week.

Some industry analysts now believe Marriott will wind up on the losing end of this battle, unless other factors besides price enter the equation.

"We don't think (Marriott) can go higher, and we would question it if they did," Canaccord analyst Ryan Meliker wrote in a research note.

Starwood’s board said it is still backing Marriot's bid while it assesses Anbang’s offer.

Marriott stood behind its last bid "as the best course" for Starwood in a Monday letter. The Bethesda, Maryland, company also advised Starwood shareholders to scrutinize Anbang's financing and consider the "timing of any required regulatory approvals."

That comment appeared to be a veiled reference to the potential hurdles that a Chinese company might have to clear to buy Starwood, which is based in Stamford, Connecticut. Marriot declined to elaborate on its letter.

Anbang dealt with similar concerns two years ago when it acquired the famed Waldorf Astoria of York for nearly $2 billion. While it tries to hook Starwood, Anbang is also trying to reel in Strategic Hotels & Resorts in a proposed $6.5 billion deal.

Although Anbang’s purchase of Waldorf was cleared by the U.S. Treasury's Committee on Foreign Investment, worries about the Waldorf becoming an outpost for Chinese espionage still hang over the hotel. Last year, President Barack Obama, his top aides and staff along with the sizable U.S. diplomatic contingent lodged elsewhere during the annual U.N. General Assembly, which takes place every September.

The switch ended a decades-long tradition of having presidents and other top U.S. diplomatic officials stay at the Waldorf when in New York. The government still leases a residence for U.S. ambassador to the United Nations in the Waldorf.

Foreign purchases of hotels and other real estate typically don’t trigger national security concerns in the U.S. unless the locations are near key military bases or other sensitive government buildings, said Anne Salladin, a special counsel specializing in national security reviews for Stroock & Stroock & Lavan in Washington.

Starwood's stable includes a W Hotel that overlooks the U.S. Treasury Department in Washington.

Caixin, a financial magazine in China, also has raised the specter of Anbang’s Starwood bid being derailed by its own government. That's because Anbang’s plans to buy Starwood and Strategic Hotels could violate restrictions that limit Chinese insurance companies from having more than 15 percent of their assets in foreign investments.

Anbang and other Chinese companies have been trying to diversify their investment portfolios by pouring into more stable locations, such as U.S. real estate, amid signs of slowing economic growth at home.

Marriott is hoping to build a hospitality empire by adding Starwood's posh hotels to its line-up. Marriott initially bid $12.2 billion for Starwood last November in a deal that would make it the world’s biggest hotel company. Marriott CEO Arne Sorenson also promised to create the industry's best customer rewards program.

The latest offer from Anbang is worth $88.66 per Starwood share. That tops the $14.41 billion offer that Marriott made last week. Anbang’s offer includes $82.75 per share in cash, which is an increase of $4.75 per share from its previous bid. The bid also includes $5.91 in stock for a spinoff of a vacation business.

Starwood's stock rose $1.62 to close Monday at $83.75 while Marriott’s shares gained $2.70, or nearly 4 percent, to finish at $71.34. (AP)