Though the $5.8 million deficit at National Public Radio was far from resolved yesterday, network management and members were buoyed by an offer of help from the Corporation for Public Broadcasting.

Late Tuesday evening, the same day Frank Mankiewicz, NPR's president since l977, announced he was relinquishing most of his responsibilities to an interim chief operating officer, CPB president Ed Pfister said, "There is no need to be bleak or pessimistic about the future outlook . . . NPR's role has been significant and CPB is deeply interested in the programs and the people we in public broadcasting serve . . . We will be searching for a way to sustain that future program of NPR."

The message was relayed to the annual meeting of the Public Radio Conference in Minneapolis by NPR board Chairman Myron Jones. The federally funded CPB distributes funds for public radio and television.

The form and amount of the assistance remained undetermined. Mankiewicz told the Washington staff via intercom from Minneapolis that the help was "a loan or something." CPB spokesmen hesitated to characterize the offer. Said one, "It's clear that CPB isn't making a dollar commitment until the stations and NPR management know what they are going to do."

Meanwhile, the conference voted to reject the NPR board's proposal that member stations pay programming fees that would have raised $1.5 million.

In the same resolution the membership urged the board to explore other fund-raising mechanisms, "such as an advanced payment of membership dues, a loan from the stations or other organizations, a transfer of community services grants to NPR programming in future years, as well as possible national on-air fund-raisers and direct mail."

In the past many stations have opposed a national effort like a radiothon because they raise money for themselves from the same listeners NPR would solicit.

Barbara Cohen, NPR vice president and managing editor for news and information, said the CPB message had calmed some of the "alarmed" member stations. She also said the membership seemed enthusiastic about continuing to pursue some of the profit-making ventures Mankiewicz had started.

"I suppose that there is some impatience, but there was never any projection that the ventures would turn any profit this year," said Cohen.

Another resolution urged the board to preserve the popular news programs "Morning Edition" and "All Things Considered," calling them "the number one programming priority."

As part of $1.5 million in budget trims, the 17-member board voted to cut parts of "NPR Plus," which debuted Jan. 3. The newscast portions of "NPR Plus" will end April 29. "Dateline," a half-hour show hosted by Sanford Ungar, will go off the air at the end of May.

"We are disappointed. We have done something new and original and all the feedback from that stations has been that the program was good," said Ungar. Ungar, who has been at NPR for more than three years, plans to leave when the show is terminated.

This week the extent of the NPR shortfall was altered from last month's original estimate of $2.8 million to $5.8 million. Part of the crisis was attributed to Mankiewicz's financial gambles, such as business ventures contingent on Federal Communications Commission approval, as well as federal reductions in public radio and television funds.

Rep. John Dingell (D-Mich.), chairman of the House Commitee on Energy and Commerce, said the administration has recommended "volunteerism" as a funding solution, and called the approach "naive faith . . . or a cynical hostility to an important national resource."

In a letter to Mankiewicz dated April 18, Rep. Timothy Wirth (D-Colo.), chairman of the House subcommittee on telecommunications, said he would introduce legislation to compensate NPR for "inflation and cost increases over the next three years."

Shortly after the budget crisis was revealed last month, NPR fired 37 employes and announced the cancellation of "The Sunday Show" and "Jazz Alive!"

The conference also passed a resolution praising Mankiewicz. Since he became president in 1977, NPR has tripled its budget and doubled its audience.

The new chief executive officer is expected to be announced later this week. The most frequently mentioned name is that of Ronald Bornstein, a former vice president of the Corporation for Public Broadcasting who is now a chancellor at the University of Wisconsin. Bornstein, according to sources, met with the NPR board yesterday in Minneapolis.