National Broadcasting Co. has decided against buying the cable channel Tempo Television for its proposed business news service but plans instead to lease time on the channel for the new programming. The General Electric Co. unit, which owns the NBC Television Network, cited tax considerations for its change in strategy. Buying the cable channel was seen as part of NBC President Robert Wright's oft-stated plans to broaden the broadcasting concern's business base. NBC announced last month it had signed a letter of intent to buy Tempo Television, and would use it for new business news and sports programming. Tempo Television, a unit of Tempo Enterprises Inc. of Tulsa, Okla., currently provides outdoors, travel and informational programming to about 12 million subscribers. NBC had planned to acquire the channel from Telecommunications Inc., a Denver-based cable operator which is in the process of buying Tempo Enterprises in a deal expected to close in the third quarter. On Thursday, NBC and Telecommunications said they were restructuring their plans to minimize ``tax and other complications that arose from trying to separate Tempo Television from its parent, Tempo Enterprises.'' Under the new plan, the companies said NBC would lease time on Tempo Television for a business news service that would run from 6 a.m. to 8 p.m. weekdays, starting in early 1989. ``Under the new arrangement, NBC will still own and manage the business news service, but will reach existing Tempo TV subscribers without actually purchasing Tempo TV,'' the announcement said. It said that Tempo Television would try to help the business news service succeed by paying the first year's affiliation fee on behalf of all current Tempo TV affiliates who continue to carry Tempo fulltime after the launch of the business news service. John Draper, a spokesman for Telecommunications, said the new arrangement ``gives NBC the same thing that they were after'' when it planned to buy the cable channel _ access to a large base of subscribers. He declined to specify how much NBC would pay for the lease. It had been reported that NBC had agreed to pay about $20 million to buy the channel. The statement did not indicate what the new plans were for introduction of the proposed sports programing that NBC previously said it would put on the cable channel. John Malone, president of Telecommunications, said in the statement that his company will ``continue to explore with NBC the best format for sports and other possible programming for a prime time and weekend service.'' Thomas S. Rogers, the NBC executive overseeing the Tempo deal, was unavailable for comment. But Joseph Rutledge, an NBC spokesman, said today that the change to a lease arrangement posed no obstacle to NBC accomplishing what it set out to do. ``Some people choose to lease a car. Some people choose to buy a car. Both people end up with transportation. We are ending up with the very outcome we sought,'' he said. The new arrangement will give NBC access to cable subscribers, a solid relationship with Telecommunications, which is the nation's biggest cable operator, and an opportunity to develop two new programming services for cable TV, Rutledge said. He said that NBC continues to talk with cable operators about what they would like to see in a sports service and that NBC hopes to begin developing sports programming for cable TV soon after the business news service goes on the air. Wright was quoted in the statement as saying, ``The cable industry has been very encouraging and we are enthusiastic about our plans going forward.''