Though it remains snarled in bookkeeping problems that have made it difficult for high-level managers to monitor it, the General Services Administration's attempt to rent out unneeded federal office and storage space has earned the government nearly $2 million in new revenue.

"This is only the tip of the iceberg," said Public Buildings Commissioner Richard O. Haase, who projected that some 10 million to 14 million square feet of office space will be added to the inventory as a result of President Reagan's executive order calling on federal agencies to reduce work space to an average of 135 square feet per person.

"At this point, we are trying to make sure we can handle the small amounts of space we already have in the inventory, because if we can't do it now with some 5 million square feet, we're going to be in one hell of a fix with 14 million more feet becoming available," Haase said.

The goal of the "outleasing" program is to make sure that cutting the size of the federal government doesn't leave vast blocks of space lying vacant. Paired with the plan to trim the average work space is an effort to move as many people as possible into government-owned space. That shuffle also will result in increasing amounts of leased space lying vacant.

"We're not going to be able to turn back all of the space to building owners, because of economic conditions," said Haase.

The National Capital Region, because it controls so much more space than any other region, has been the most active.

"We've been very successful," said Kenneth L. Perrin, head of the GSA utilization branch in the NCR. "When we began, we had an annual income of $490,000; now we're at $1.4 million."

Perrin now has 20 blocks of space totalling nearly 100,000 square feet available for lease. In the next several months, another 70,000 square feet will be available in this area, he said.

"As the market becomes less soft and the economic recovery continues to improve, people are begining to expand their offices more," Perrin said. "That is especially true here in Washington."

Because GSA generally signs long-term leases for office space, the rates that it gets are often very favorable. Thus, when it sublets, it usually can do so at a profit.

Right now, about 90 percent of the sublet rents are above what GSA is paying, Perrin said.

"We try to only outlease for more than it costs us, but in some cases that isn't possible," he said. But when that happens, it isn't a total loss, he added, because if the space were not sublet, the government would be losing the entire rent it pays.

Assessing how the program is doing nationwide is harder than going to a single region because of the record-keeping problem. It is still impossible to determine, for example:

* How many outleases GSA has for government-owned space and for commercially leased space, and how much revenue those leases are producing.

* How long the space has been vacant working its way through the bureaucracy to the leasing staff.

* How many groups are receiving free space in federal buildings under various provisions of the law. Included in this group, for example, are federal credit unions and recreation associations.

Perrin said that each block of vacant space in Washington costs the government an average of about $15 a square foot.

At the upper echelons of GSA, policy makers such as Haase track the program against a target of having 80 percent of the space available rented out.

But at Perrin's level, that's unrealistic.

"Haase, and the others up there, may not like to hear this, but that target is not meaningful," Perrin said. "I don't think any percentage of what we have vacant is a realistic target. The target has to be based on how we are actively trying to mitigate our government losses; how we're marketing the space."

Here are the largest blocks of space available currently, the square footage and the term of the lease:

* 2001 S St. NW, 15,145 square feet (three floors), Jan. 1985.

* 5225 Wisconsin Ave. NW, 13,502 sq. ft., Oct. 1984.

* 1730 K St. NW, 8,570 sq. ft., Sept. 1985.

* 1020 11th St. NW, 6,820 sq. ft., May 1990.

* 1717 H St. NW, 7,253 sq. ft., July 1985.

* 6550 Belcrest Rd, Hyattsville, 7,175 sq. ft., July 1993.

* 1825 Connecticut Ave. NW, 7,025 sq. ft., Jan. 1985.

* 425 13th St. NW, 4,805 sq. ft., Mar. 1985.

* 2100 M St. NW, 4,664 sq. ft., Nov. 1986.

* 1111 20th St. NW, 4,050 sq. ft., Oct. 1989.