ABC announced a new format for its lagging Evening News yesterday, establishing Washington as the network's key "news center," dropping co-anchor Harry Reasoner from the cast and putting WTOP anchorman Max Robinson in charge of the "domestic desk" in Chicago.

In establishing four major "news desks" in Washington, London, Chicago and New York, ABC News President Roone Arledge said anchorwoman Barbara Walters will handle "a special coverage desk" in New York where she'll be doing little reading of news and be more involved "in making news herself."

It marks the first time a network news show will not have an established New York anchor.

Under the new format, which will not be seen on the air until sometime this summer, Frank Reynolds of the ABC bureau here will head the "national desk" in Washington. Correspondent Peter Jennings will be in charge of the "foreign desk" in London, in addition to the Robinson and Walters assignments.

Howard K. Smith, said Arledge, will continue to do commentaries three time a week.

Arledge said Reasoner will continue as an anchorman for ABC for a while but will not appear on the show after the changes take effect. He said it was no secret that Reasoner has been unhappy with his role at ABC, but refused to say whether Reasoner would be let out of the remaining two years of his $500,000-a-year contract.

Reasoner reportedly has an open invitation from CBS News to return to that network as a replacement for chief correspondent Bill Moyers, who will leave CBS Reports later this year for the Public Broadcasting Service.

"We're discussing what (reasoner) wants to do with his future." Arledge said. "I don't want it to come out that we're being cruel to poor Harry." he added, mentioning the television net work tradition of holding people to switch contracts when they want to switch to another job elsewhere.

Reasoner has claimed he had an oral agreement with previous ABC News president William Sheehan to leave this August.

Arledge had special praise for Robinson, who has been a top anchorman at Channel 9 here for the past nine years and who joins ABC in June, when his current contract expires.

Arledge said that (since) "important news events . . . often occur in the heartland of the nation and too often their significant is under-reported . . . we have given this assignment to Max Robinson, who joins us after a highly successful career as a Washington, D.C., TV journalist. He has that sense of community news that will benefit our viewers as he covers the great mass of stories that happen in Mid-America."

Arledge said that under the changes. "We will make Washington the focal point of our news broadcast," although production control of ABC News will remain in New York for the foreseeable future.

He said there would be no regular New York anchor because "very little of the news takes place in New York."

ABC, which leads CBS and NBC in entertainment and sports ratings, has always languished in third place as a news network.

When Walters was hired for $1 million a year in 1976 and Arledge later added the news presidency to his role as head of sports, many critics suggested het network was going to attempt to lift its news rating through big names and breezy broadcasts.

At yesterday's press conference, reporters had a little trouble sorting out just what ABC does have in mind.

At one point, Frank Reynolds took pains to praise Walters' credentials as a news reporter, adding that "We are not going to let personalities get in the way of the news."

But Arledge, in his prepared statement, had suggested Walters' new assignment "will become a source of news itself.

"Barbara Walters," said Arledge, "is not only an outstanding journalist, reporters with her unmatched ability to draw insights and information from those who are in the news at every level, from heads of state to those simply involved in life's daily events."

Later he told reporters that "We want to get our heavyweights (like Walters) to the scene of stories."

The reason is not that the "heavyweights" have audience recognitition or star quality, but that they bring special talents to a story, Arledge said.

Arledge and other ABC executives defended their present Evening News against charges that it is heavy on chitchat.

Arledge claimed that several surveys had shown ABC has more hard news than the other two networks.

Arledge, who refers to the new team as "chief correspondents" rather than as "anchors," insisted yesterday that he'd never said he wanted to eliminate the anchor role or concept entirely.

Rather, he wanted to change the nature and role of the anchors and get them out of the studio, he said.