Blue Cross has offered to put its financial clout behind the efforts of a local watchdog agency to lower health care costs in Northern Virginia.

Richard Groppe, manager of health planning and research for the Washington-area Blue Cross company, told a Northern Virginia health planning agency last week that Blue Cross would consider withholding reimbursements to hospitals and other health facilities that the health planning agency feels are not needed.

"Group Hospitalization Inc. (the local Blue Cross) makes up between one-third and one-half of a hospital's business," Groppe said. "We would be willing to impose financial sanctions against new health facilities or additions that your group finds unnecessary for Northern Virginia and contributing to higher health care costs."

Northern Virginia's health planning agency, the Health Systems aAgency of Northern Virginia, is a federally mandated organization responsible for evaluating health care needs in this region and containing the rising costs of health care, partly caused by an excess of health facilities. But the agency has no more than an advisory role. The Virginia State Health Commissioner ultimately authorizes new health facilities, whether they involve building a new hospital wing or purchasing a sophisticated piece of equipment for cancer detection.

Blue Cross interest in health planning results from the company's decision to pass higher health care costs on to their clients. A Blue Cross spokesman said the company has not lost customers yet as a result of more expensive health insurance plans, but foresees losing clients in the future if costs continue to increase. He added that some clients now are buying less conerage.

"We're going to our group plan clients with contracts for plans that cost between $140 and $150 a month," Groppe said. "We can't tolerate that level of cost."

Blue Cross refusal to reimburse hospitals for patient bills could force a hospital out of business.

"If somebody planning to build a hospital doesn't have guarnatees from Blue Cross to provide reimbursements for patient bills, he's going to have a hard time getting financed to build it," Groppe explained. "We would like to tie our reimbursement s to your decisions on what hospital facilities are needed or not."

Blue Cross recently announced it would provide reimbursements to only one of two hospitals proposed for the Maryland suburban area. As a result only one of the two hospitals is expected to be built. The two groups sponsoring the hospitals proposed for Montgomery County, Shady Grove Adventist Hospital and the Gaithersburg Community Hospital, now are "negotiating the problem between themselves," Groppe said.

"We have worked with the Maryland health planning groups very successfully, and some of our efforts costs down," Groppe added. "We would like to do the same with Northern Virginia."

The public hearing tuesday wa one of three being held to gain comments from groups and individuals on health care needs for Northern Virginia. Public comment will be considered by the health agency as it develops its master plan for the growth of health care facilities in the area, a health agency spokesman said.

The two remaining public hearings both will be held 10 a.m. Saturday. One will be at Herndon High School, 700 Bennett St. in Herndon and the other in room 303-A at the Woodbridge campus of the Northern Virginia Community College, 15200 Smoketown Rd. Woolbridge.

The health agency, one of more than 200 created by the National Health Planning and Resources Development Act of 1974, is required by federal law to develop a comprehensive health care plan for Northern Virginia. Drafts of the plan will be submitted to public hearing in the spring, and final versions are expected to be completed by late summer, the health agency spokesman said.

The plan will identify what health facilities are needed in Northern Virginia, where they are needed, what excess of health facilities are in the area and methods to curtail growth of unneededfacilities.