Blue Cross/Blue Shield, which provides health insurance coverage for six of every 10 U.S. workers here, says it may have to pull out of next year's federal health program unless it is allowed to cut benefits for treatment of mental and nervous conditions.

The plan -- which covers 5 million federal workers and their dependents nationwide -- provides one of the most attractive benefit programs in government in the area of mental health. Of 447,000 federal workers and retirees (not counting dependents) in this area covered by the Federal Employee Health Benefits Program, 283,000 are currently enrolled in the Blues' program.

Blue Cross/Blue Shield's high option plan now pays all hospital and related costs for 365 days of inpatient treatment for mental or nervous disorders. It now covers unlimited outpatient visits and pays 70 percent of the "usual, customary" charges for mental health services from psychiatrists.

The insurance plan proposes to cut back mental benefits to 60 days of hospitalization a year beginning in 1982, and to put an annual limit of 50 outpatient visits in its plan, in addition to reducing its share of payments to psychiatrists.

Federal employes now pay $793.52 a year for high-option family coverage and $385.84 a year for individual Blues' plan coverage. The government pays $926.64 for family coverage under the high-option plan and $396.46 a year for those with individual coverage.

Blue Cross/Blue Shield officials say the average benefit the company paid out in 1980 for federal workers receiving mental and nervous disorder treatment was $1,620.

The Office of Personnel Management, negotiating for the government, has given all 130 plans in the government program until Friday to come up with benefit-premium packages that meet its requirements. OPM has cut back benefits an average of 16.5 percent in a move it says is designed to hold down premium increases and keep government costs in the plan from skyrocketing. Uncle Sam pays about 60 percent of each employe's average premium. Amounts actually paid by workers range from $200 to nearly $800 per year, depending on the plan and coverage desired.

OPM has tentatively approved mental health benefit cutbacks requested by Blue Cross/Blue Shield for its 1982 health insurance package. But heavy pressure from government workers who depend on mental health benefits for themselves and their families, and the powerful psychiatric community has persuaded some members of Congress to introduce legislation that would, in effect, freeze benefits for mental treatment at current levels through 1982.

Sen. Alfonse D'Amato (R-N.Y.) has added a rider to the Treasury, Postal Service and General Government Appropriations bill that would require plans such as Blue Cross/Blue Shield to keep 1982 mental health benefits at current levels.

Blue Cross/Blue Shield officials yesterday sent a letter to the Senate, urging it to defeat any attempt to freeze mental health benefits. Unless this is done, the letter from President Walter J. McNerney said, the giant insurance company might be driven to "the point where we probably would be unable to underwrite" either its high-option or low-option plan next year.

The company estimates it will "lose" $275 million on its federal program this year. It says its cost in mental benefits paid out is $156.5 million, or nearly 8 percent of its total benefits paid.

D'Amato's office said it had not yet received the Blue Cross/Blue Shield letter. OPM officials said they plan to wrap up negotiations on all 1982 health insurance plans by Friday, and they do not anticipate Congress acting in time to freeze benefits.