Marriott International is buying rival hotel chain Starwood for $12.2 billion in a deal that will secure its position as the world's largest hotelier.

The stock-and-cash deal, if completed, will add 50 percent more rooms to Marriott's portfolio and give it more unique, design-focused hotels that appeal to younger travelers.

The new company will have 5,500 properties with more than 1.1 million rooms around the world, uniting Starwood's brands, which include Sheraton, Westin, W and St. Regis, with Marriott's two dozen brands, including Courtyard by Marriott, Ritz-Carlton and Fairfield Inn.

The next-largest hotel company is Hilton Worldwide, with 4,400 properties and about 720,000 rooms.

In April, Starwood announced that its board was exploring strategic options for the hotel company. The Stamford, Connecticut, company has struggled to grow as fast as its rivals, particularly in "limited service hotels" - smaller properties that don't have restaurants or banquet halls. They are often located on the side of the highway, near airports or in suburban office parks.

There had been speculation in the markets about a potential deal with Holiday Inn owner Intercontinental Hotels Group and, more recently, Hyatt Hotels Corp.

The deal comes at a time of record hotel occupancy and rates.

During the first nine months of the year, guests filled 67.3 percent of the available rooms in the United States, according to research company STR. That's the highest level since STR began collecting data in 1987. Guests paid an average of $120.35 a night so far this year. The previous record, adjusted for inflation, was $119.70 in 2008.

Marriott, based in Bethesda, Maryland, has been aggressively growing. In April, it acquired Canadian chain Delta Hotels and Resorts, helping it become the largest hotel company in Canada.