Traders stand by the post where the stock for Starwood Hotels & Resorts Worldwide Inc is traded in this 2015 file photo.  (Reuters/Brendan McDermid)

Marriott International’s $12.2 billion cash-and-stock deal to take over Starwood Hotels & Resorts and become the world’s largest lodging company is suddenly not so certain.

Starwood on Monday said it received an unsolicited offer from a consortium of companies led by China’s Anbang Insurance Group to buy the Stamford, Conn.-based hotelier for $12.8 billion, or $76 per share, in cash. That represents a 7.9 percent premium on the stock’s Friday closing price of $70.42.

Anbang two years ago purchased the Waldorf Astoria New York hotel for $1.95 billion from Hilton Worldwide. It also is closing in on a $6.5 billion deal to buy Strategic Hotels & Resorts, a Chicago-based company that owns luxury hotels operating under brands like the Four Season, Ritz-Carlton, InternContinental and Loews, the Wall Street Journal reported Sunday.

Chinese investors have begun buying up billions of dollars of U.S. real estate amid worries of an economic slowdown in the world’s second-largest economy. Anbang, which began as a Beijing-based car insurance company in 2004, has expanded aggressively in recent years, buying up insurance firms and banks in Belgium, South Korea, the Netherlands and the United States. The company’s chairman is said to have personal ties to Deng Xiaoping, China’s former top leader, that have helped propel it from a $75 million company in 2004 to a powerhouse with roughly $25 billion, according to company website in assets. Anbang has 30,000 employees and 35 million clients around the world, according to its website.

Analysts said Anbang has offered few details about its plans for Starwood. Marriott called the consortium’s bid “highly conditional and non-binding.”

“Anbang is really the big unknown,” said Jim Butler, head of global hospitality and Chinese investment groups at the law firm Jeffer Mangels Butler & Mitchell in Los Angeles. “They spent a lot of money on the Waldorf and made a big splash, but nobody knows what they’re going to do or what this all means.”

Marriott said it had given Starwood permission to engage in discussions with Anbang until the end of the day Thursday.

“Starwood stated today that its Board of Directors has not changed its recommendation in support of Starwood’s merger with Marriott,” Marriott said in a statement Monday.

Shareholders of Starwood and Marriott are set to vote on the proposed deal on March 28.

If Starwood were to end its agreement with Marriott or withdraw its recommendation to stockholders to vote in favor of the deal, the company would be obligated to pay Marriott a $400 million termination fee in cash, according to Marriott.

“The Marriott deal was two shareholders votes and two government approvals away from closing,” said David Loeb, a lodging analyst for Robert W. Baird & Co. “Now there are a number of complexities involved.”

The Anbang consortium also includes Primavera Capital Group and J.C. Flowers & Co., a New York-based private equity investment firm. Primavera is a China-based private equity firm founded by Fred Hu, an economist who was formerly chairman of Greater China Group of Goldman Sachs.

“It’s one thing to be an economist and write certain views, and it’s another thing to put your money where your mouth is,” Hu said in a 2010 interview about his move to Primavera after 13 years at Goldman. He said then that he was focusing on China’s financial sector and cross border mergers and acquisitions. One of his most notable successes was an early investment in the Alibaba Group, before the Internet search and retailing company went public.

But analysts seemed skeptical that Starwood, whose brands include St. Regis, Sheraton and W Hotels, would accept Anbang’s bid. The hotel company, which essentially put itself up for sale last year, was reported to have talked to a number of potential suitors before choosing Marriott.

“Starwood had several offers and very fluid conversations with a dozen companies before they even announced Marriott was the winner,” said Chad Beynon, an analyst for Macquarie Securities in New York. “The bottom line is, Starwood wants to be with Marriott and I don’t think the offer is high enough to start a bidding war.”

In addition to standard regulatory approvals, a deal between Anbang and Starwood would likely require a go-ahead from the Committee on Foreign Investment in the U.S., the same body that approved the company’s purchase of the Waldorf Astoria.

“The key issue in any real estate deal or the purchase of any hotel is going to be proximity: Are the assets close to a sensitive government facility or installation?,” said Anne W. Salladin, special counsel at the New York law firm of Stroock & Stroock & Lavan. “One question is, would there be ability for someone to collect information through espionage of some sort?”

Staff writer Steven Mufson contributed to this report.