Marriott Corp. outbid a competitor from Hong Kong and agreed yesterday to buy Host International Inc. of Santa Monica, Calif., for $149 million in cash.

The two companies said they have agreed in principle to merge but still must work out several details, including termination of an earlier agreement Host had made to be acquired by DFS Group Ltd. of Hong Kong.

To acquire Host, Marriott agreed to pay $31 each for all of Host's 4.8 million shares, topping a $29.25 bid made last week by DFS. Host's board of directors accepted that offer but changed their minds after Marriott raised the ante.

Merger of the two companies would make Marriott the preeminent purveyor of food to travelers in the United States.

Marriott is already the biggest supplier of in-flight meals to airlines and Host is the largest operator of restaurants, bars and gift shops in airports. Host also supplies a few airlines with food and Marriott has some terminal food-service franchises.

Wall Street analysts called the separate operations "a good fit" and said a merger will give Marriott increased efficiencies that should translate into higher profits for its fast-growing contract-food business.

The biggest cost of an airport or airline food operation is setting up a central commissary to prepare food in large quantities. The same commissary can serve both airport restaurants and flights from that airport.

The merger will have to be reviewed by the Department of Justice and Federal Trade Commission to assure that it does not reduce competition in travel-oriented food services.

However, stock specialists who follow the two companies said Host's share of the in-flight airline feeding market is so small that a takeover by Marriott would have little impact on rivals in that business.

Second only to hotels among Marriott's $1.7 billion-a-year operations, contract-food services produced $529 million of sales and $39.8 million of profits last year for the Bethesda company.

Host earned a slim profit of $14 million on sales of $357 million last year with the bulk of its business at food, drink and gift concessions Host operates in 16 of the nation's 25 busiest airports, including Baltimore-Washington International.

Yesterday's joint merger announcement ended a month of bidding for Host, which had not even been considered a takeover target before the bidding began.

On Nov. 1, Host announced it had agreed to be acquired by DFS -- the initials stand for duty free shops -- which runs most of the duty-free shops in airports in the Far East. DFS was to pay $24.25 a share for Host.

Seeing a potentialy attractive acquisition falling into the hands of a new competitor, Marriott made an unsolicited bid of $29 a share for Host on Nov. 21. When DFS topped Marriott's bid by 25 cents a share and signed a preliminary agreement with Host, Marriott responded with the $31 offer.

Host earlier granted DFS an option to about 875,000 shares of its stock for $29.25 and agreed to sell DFS the duty-free shops it runs in New York City airports and some other operations.

The joint announcement said Marriott "has agreed in principle to recognize" the options Host gave DFS, but neither company would clarify the statement. Marriott probably will pay Host the $1.75-a-share difference between Host's option price on the 875,000 shares, but whether Host will sell its duty-free shops to DFS could not be determined.

Marriott and Host first got together a couple of years ago when Marriott sold Host a group of unprofitable "dinner house" restaurants here, including the Joshua Tree and Phineas chains. Host has remodeled, remenued and renamed the restaurants and is now running them at a profit.

Besides its BWI food concessions, Host's operations in the Washington area include the Casa Maria restaurants in McLean, Alexandria and Washington, Barclay's in Fairfax, Carnegie's in Alexandria, Phineas in Rockville and Charley's in McLean, Springfield and the District.