United National Bank, one of two black-owned commercial banks based in the District, marched into the heart of the city's growing K Street NW business and financial corridor yesterday by opening a new three-level headquarters in the International Square complex.

Following formal ceremonies that opened the office, at 19th and K Street, bank president Samuel L. Foggic said he would wage extensive competition with banks and savings institutions that already dot nearly every K Street corner - seeking additional resources to fund new business and home mortgage investment in more depressed sections of the city.

Organized in 1964. United National has been identified primarily with Northeast Washington. Its main office previously was located at 3940 Minnesota Ave. NE (Which becomes 2 branch). Branches were opened earlier this decade at Howard University and on Rhode Island Avenue.

The minority institution has been one of the fastest-growing D.C. banks in the past year in terms of percentage growth, with deposits up to $30 million from $23 million on Jan. 1. Total assets now exceed $35 million.

Foggie said United's decision to compete more actively for retail and commercial business outside the Northeast community was based on "the hope that this will afford us a greater market to continue what we've been doing."

Specifically United and other black financial institutions have been concentrating their loan funds in neighborhoods that established banks avoided in the past.

The United officer said that while this pattern is changing with bigger banks now investing in the less affluent sections of Washington, a big and "good market" needs greater banking services.

Of a $16 million loan volume, United has $5 million of consumer loans and $4.5 million in home mortgage loans, mostly for consumers in Northeast. Foggie also noted that many current United customers already work in the downtown area and he said the new office will serve these customers.

Foggie said United has the distinction of being the city's only commercial bank with a computer system that links every teller in every branch. Thus, desposits made at one office are recorded instantaneously in all offices, avoiding delays in balancing customer accounts.

City Council chairman Sterling Tucker and Del. Walter E. Fauntroy (D.D.C.) took part in the ribbon-cutting yesterday. Open houses are planned Saturday at all United offices.