National Public Radio, facing severe cuts in federal funding, yesterday announced that it vigorously intends to seek new private-sector contributions to public broadcasting.

"We're prepared to enter into almost any profession, except the oldest one," NPR President Frank Mankiewicz told a noon press conference at the network's downtown offices. "We intend to produce an entirely different source of revenue within the next five or six years."

He portrayed a grim bottom line that would leave NPR with 50 percent lower federal funding (through the Corporation for Public Broadcasting) in 1986, when current forward funding runs out.

In pursuit of new funding, Mankiewicz said, NPR has hired a major public relations firm, the Hannaford Co., to coordinate a series of presentations to corporations and foundations around the country. Hannaford's head is Peter Hannaford, whose former partner is Michael Deaver, deputy chief of staff to President Reagan. Hannaford, who counts among his other clients the New York Stock Exchange, is himself a former Reagan campaign adviser and intimate. Mankiewicz, former press secretary to George McGovern, smiled when he said, "Pete Hannaford is not unknown in this city." Newsman Daniel Schorr asked whether Hannaford was working for free, and Mankiewicz said he was "receiving less than he would otherwise."

The income-generating activities outlined by Mankiewicz included "a new and invigorating underwriting campaign," cost-sharing on NPR's satellite, sales of cassettes of NPR programs and other projects. "We're going to remind them that President Reagan has said the private sector will make up the difference," said Mankiewicz. "We intend to quote the president liberally to that effect. We'll use his words a lot, hoping they will feel a responsibility to increase their participation in public broadcasting, and particularly, public radio."

There are already task forces of prominent business leaders at work in Los Angeles, Chicago and New York (the last headed by TWA president C.E. Meyer Jr.) to effect NPR's five-year plan to be "entirely funded by other than federal sources," according to Mankiewicz.

NPR's reduction in federal funding forced the issue, said Mankiewicz. " NPR is a very fragile system, and something needs to be done."

NPR's new funding plan revolves around separate news/information and performance funds that will sell underwriting shares to corporations and foundations -- for instance, $250,000 each for 20 available for the news section. Credits will then be spread across all NPR programming, Mankiewicz explained, thereby making it more attractive for the underwriter. The funds will be used entirely to support NPR's national programming services, which this year received $14.5 million in government support, while NPR's 255 member stations received $19 million in federal funding. Under the new plan, said Mankiewicz, "government funds will shift to the stations; they need it the most."

Mankiewicz said NPR has already been approached by several companies wanting to use the network's satellite on a cost-sharing basis. "We pay $3 1/2 million a year now. The users will pay the cost, which will free those funds for other uses." Other possibilities include cable audio and teletext services. He added that NPR would even consider entrepreneurial activities outside the broadcasting field. "We're the first 'formerly federal grantee' to embark on this step. It's fairly thin ice out there. We're happy to be out there first because we can make some figures that nobody else has drawn. On the other hand, nobody else has been out there to show where the cracks are. It's chancy, but it's the only way we can go."