New York City's three major newspapers - the morning Times and Daily News and the afternoon Post - were struck late yesterday by the 1450-member local pressmen's union. The three papers called off publication of today's editions but did not rule out future attempts to publish.

"We suspended publication as of now," said John Pomfret, assistant general manager of The Times.

Picket lines went up at the three papers after they announced intention to post new work rules in their pressrooms.

The announcement followed the breakdown of day-long negotiations between the two sides and efforts by federal mediators to head off a strike. The main issue dividing the two sides involved who should control the rules governing the number of workers needed to run the newspaper presses.

The publishers of the three papers, whose total daily circulation exceeds 3 million, had said they had contingency plans to publish in the event of a strike, but apparently decided not to do so because of difficulties in getting the papers delivered.

The pressmen's union has received solid support from eight of the nine other newspaper craft unions and the Newspaper Guild, which represents reporters and editors. Only the printers had declined to back the pressmen, because their union has a long-term contract that bars any strikes.

Support from the Newspapers Delivers' Union was considered particularly crucial, since the three largely automated newspapers have the capacity to publish without union help but can't get their pages to homes and newsstands without the cooperation of the deliverers.

The strike is the 12th for New York City newspapers since 1950. Two protracted strikes in the 1960s led to the demise of a number of New York City dailies, including the Mirror, The Herald Tribune, The Journal and the World-Telegraph Sun.

William Kennedy Jr., president of Printing Pressmen's Union No. 2, said the publishers had deliberately provoked a strike by posting the work rules and had, chosen a slow season. The pressmen's contract expired last March 30 and there have been off and on negotiations since then.

"The publishers are seeking increased profits and have brought the strike on themselves," said Kennedy.

H. J. Kracke, executive director of the Publishers Association of New York, which has become a negotiating front for the three newspapers, said the decision to post the work rules had been taken because there was "no significant progress" in the talks.

A deadline for posting the work rules had been extended for 24 hours at the request of federal mediators was made again yesterday but the publishers declined to delay further.

Kracke said the new work rules were needed to provide the publishers with flexibility in manning and scheduling their press operations in order to make them economically competitive with newspapers in the suburbs. He said that any reduction in the number of people employed in the pressmen would come only through gradual attrition and not through lay-offs.

Union chief Kennedy claimed the reductions being sought by the newspapers amount to 50 percent of his membership. There are 700 pressmen employed at the News, 650 at the Times and about 200 at the Post.

Kracke denied the newspapers had a 50 percent target. He expressed hope that the negotiations with the pressmen would continue. But Kennedy said they had broken off entirely and would be "starting from scratch" if and when they were resumed.

Martin Fischbein, a spokesman for the Post, said that "at least for tomorrow there will be no New York Post, but if the drivers cross the lines, then it's another question."