When New York's newspaper stike began 12 weeks ago, the three publishers vowed solidarity forever. But as it draws to an end, the facade of unity has long been discarded, and yesterday the New York Post filed suit against the Daily News.

Post publisher Rupert Murdoch alleged that the News conspired with the newspaper deliverers union to prevent him from bringing out a new morning tabloid, the New York Daily Sun, that would have competed with the News.

The Post seeks $75 million in treble damages for alleged violations of antitrust laws and a court order prohibiting the News and drivers from any further actions against the unborn Sun.

Murdoch broke with the New York Times and Daily News to settle the pressmen's strike and resume publication Oct. 5.

Two weeks later, Murdoch announced that he would launch the Sun, a morning tabloid obviously aimed at taking readers and advertisers away from the Daily News.

The Post's suit charges that the News threatened to eliminate drivers' jobs at the News if "the Sun were allowed to appear" and that Douglas LaChance, the head of the drivers' union, refused to consider distribution of the Sun "except upon terms acceptable to the news."

Jonathan Thompson, a spokesman for the Daily News, said the News never threatened to lay off drivers in retaliation for the appearance of the Sun.

The News and drivers have an agreement that the drivers cannot provide a better deal to any other paper than the union provides the News. LaChance initially agreed to let Murdoch deliver the Sun by wholesaler and thereby save money. LaChance changed his mind after the News said there were parts of the city in which it might want to use wholesalers.