Another effort by federal mediators to resolve the public employes contract dispute in Prince George's County ended abruptly yesterday, as union officials charged that County Executive Lawrence Hogan was seeking a strike and Hogan claimed that parts of the proposed contract would "benefit only the union leaders."

Union officials said they had come to the mediation session in downtown Washington expecting to reach a settlement, only to discover that Hogan, upon reading a tentative contract, objected to several of its provisions.

"He came with another 12 items, some of which were never brought to the bargaining table," fumed Ernie Crofoot, Maryland director of AFSCME, the public workers union. "We have spent 12 months of our time. . . tens of thousands of dollars and lawyer costs, and we're sitting here now with zilch, with absolutely nothing."

Hogan's office, in return, issued a press release stating that the mediation session ended because the union was demanding that the contract include items "that benefit only the union leaders." The statement said that on other economic issues the county had agreed to compromise.

For the last year, the county and the 1,500-member union have been trying to negotiate a new contract. Since July, when the last contract expired, county employes who guard the county jail, operate snow plows, fix roads, inspect new buildings and provide secretarial services to every county office have been without the cost-of-living increases given non-unionized county workers.

Two weeks ago, the dispute appeared to be resolved when Hogan's negotiating team and the union signed a tentative agreement that gave the employes a 4.7 percent wage increase this year and 5 percent next year.

However, Hogan rejected the agreement, according to several sources, because he was angry at recent public criticism of him by the county council and the union. At a meeting with his negotiators after the tentative agreement had been signed, Hogan said he would not approve anything if it appeared that he had capitulated to the council or to union pressure, sources said.

Several days after the meeting, Hogan said he would not approve the tentative agreement, which the union membership had already ratified, because of economic considerations.

It was those economic considerations, including a cash bonus to employes and the county's share of some minor medical costs, that the union and county were supposed to discuss with the federal mediators yesterday.

Crofoot said after the meeting that when the county's negotiating team brought up 12 new issues, he become convinced that Hogan did not want to settle with the union. "We are dealing with something so irrational here that I can't even explain it. I've never encountered anything like this."