The twin-tower Baltimore Hilton, a cornerstone in the city's Charles Center downtown urban renewal project, has been sold tentatively to a group of Arab investors at an undisclosed price.

Developer William L. Siskind, who will retain ownership of other Hilton franchises in Annapolis and Pikesville, said the sale will assure the continued viability of the Financially troubled downtown hotel.

"It takes, at this point, an injection of a couple of million dollars, which these people are willing to give," said Siskind, a major developer in Baltimore's acclaimed inner city renaissance.

He said the Hilton's problems to date have stemmed from a lag in completion of other downtown projects likely to push its occupancy rate above its present level of 55 percent. These projects include a new convention center, scheduled for completion in 1980, and the Baltimore subway, with an entrance adjacent to the hotel planned to open in 1983.

Siskind built the first tower containing 23 stories in 1968 and a second, 30-floor adjacent tower in 1974. Wigh a total capacity for 702 rooms, the Hilton became what Siskind said was the only "new firs class" hotel built in downtown Baltimore in decades.

He added that the new owners include the abu Ghazaleh family, which owns a chain of food stores throughout the Middle East, and a second family from Kuwait. Members of the investment group also own hotels managed by the Sheraton, Meridian and Marriott Chains in Egyp, Saudi Arabia, the Sudan and Kuwait.

Under the tentative financial agreement, the new owners will assume two bank loans and a city government loan originally made to Siskind. In addition, the new investors the hotel. A Boston firm, CSC Hotel Consultants, will manage the hotel.

Siskind said his compensation will be deferred for five years under the proposed agreement.