In the first major breakthrough in The Washington Star's negotiations with its labor unions, a key Teamsters local has agreed to present a compromise contract proposal to its members for possible ratification.

Plans for the vote on the porposed five-year labor contract-scheduled to be held Satuday-were announced yesterday by Local 639 of the International Brotherhood of Teamsters, which represents delivery truck drivers and other circulation employes at The Star. A Star spokeswoman said the newsapper's management would have no comment on the contract negotiations.

Ronald L. Warren, business representative for Teamsters employes at The Star, expressed uncertainty about whether the proposed contract would be ratified. He said that Star negotiators had offered some concessions but described these as "not enough to make me happy." Warren said he had not decided whether he would urge union members to ratify or reject the proposed contract.

Eleven labor unions representing about 1,270 full-time Star employes have been engaged in intensive negotiations to complete stringently modified new contracts in the face of a Dec. 31 deadline. Time Inc., the publishing company that purchased The Star earlier this year, has threatened to close The Star on New Year's Day if acceptable contracts are not approved before then.

Teamsters Local 639 is among The Star's largest employe unions. The proposed Teamsters contract scheduled for a Saturday vote would set terms for nearly 300 circulation route managers at The Star. Warren said negotiations have not yet concluded on proposed contracts for two smaller Teamsters units at The Star.

Leaders of other major unions representing Star employes have reported widely varying developments in bargaining sessions in recent days.

Talks between The Star's management and Columbia Typographical Union No. 101, which represents about 175 Star printers, were broken off on Dec. 12 and have not resumed, according to union officials. William Boarman, the CTU's president, said negotiations ended amid wide disagreements centering on The Star's proposal to eliminate 80 printing jobs by June and to reduce the printing staff to a few as 25 jobs during the next five years. "We told them that we couldn't enter into any agreement that would call for forced retirements," Boarman said.

Officials of the Washington-Baltimore Newsaper Guild, which represents abokut 475 news, advertising, clerical and other white-collar employes, have reported considerable progress in their negotiations, but said yesterday that major obstacles remain. A key issue, Guild officials say, is management's demand for the right to deny any pay raise during the next five years to 10 percent of The Star's highest-salaried employes.

Bargaining between The Star and the Newspaper and Graphic Communications UnionLocal 6, which represents anout 85 full-time Star pressmen, resumed on Monday and continued yesterday. The talls had broken down temporarily last week. Raphael F. Collins, secretary-treasurer of Local 6, said Tuesday, "We are still pretty far apart but we're working towards a solution."

Several smaller unions are reported by union officials to be close to settlements on new contracts.

According to Teamsters representative Warren, a central issue in the Teamsters' negotiations with The Star has been what union officials view as a threat by management ot start replacing Teamsters employes with non-union workers. Warren said The Star agreed to guarantee that no current Teamsters employe would be laid off, but refused to assure the union if would hire union, rather than nonunion, workers to replace Teamster employes who resign or retire.

"Thy mad a decent wage offer," Warren noted. He said that route managers, who currently earn $289 a week, would receive $40 increase in weekly pay and fringe benefits in the first year of the proposed contract. The increase would be $39 in the second year and $40 in the thrid, he said.