The drive to break the Senate's month-long filibuster against the administration's labor law revision package stalled yesterday, casting new doubt over the fate of the union-backed measure.

Sponsors of the controversial bill picked up no new votes yesterday, and failed for the fifth time to cut off debate. The vote was 58 to 39.

After the vote, Sen. Mark O. Hatfield (R-Ore.), heretofore a staunch filibuster foe, warned that his vote can no longer be taken for granted.

Hatfield's warning, coupled with the fact that this was the first time that the bill's supporters failed to gain ground from one vote to the next, pointed to trouble - some said deep trouble - for the entire package.

But Senate Majority Leader Robert C. Byrd (D-W. Va.) calmly ordered another cloture vote for next Tuesday or Wednesday, and labor lobbyists continued to insist they would eventually have the votes to choke off the talkathon.

Sources on both sides indicated that, with at least four days for regrouping, handholding and armtwisting, the outcome is too close to call. But there was widespread agreement the next week's votes may be decisive and that the administration, the Senate Democratic leadership and organized labor have, as one lobbyist put it, "a helluva lot of work to do in four days."

The bill, which would generally make it easier for unions to organize workers and win contracts, for two days has been stymied two votes short of the 60 needed to invoke cloture and the filibuster.

Wednesday's vote was 58 to 41. On each previous vote, the antifilibuster forces had picked up votes. They had hoped to break off the debate by Wednesday, a deadline that was largely self-imposed but important in the sense that it established a yardstick for testing their strength.

The previous record for cloture votes on a single issue, substantive or procedural, was six during a debate in 1975 over a contested senatorial election in New Hampshire.

The Senate has taken up vistually no other business since the labor bill debate began May 16, prompting Hatfield's unexpected assertion that he may not support cloture attempts after the sixth try.

"As one senator, I just say I'm reaching the point of diminishing returns," Hatfield told the Senate after yesterday's vote. "I, for one, do not want to be responsible for holding up the Senate ad infinitum. My support of cloture cannot be taken for granted, because of other vital legislation." He said he would probably support the next cloture motion, but can't be counted on after that.

"I'm growing weary of pushing vital legislation to the end of the session and having it passed in the wee hours of the morning," he added.

Byrd said he sympathized, and suggested that cloture was the way to get on with the Senate's business.

Hatfield told a reporter that two senators told him afterward they agreed with him.

The antifilibuster forces may have also lost ground with Sen. John J. Sparkman (D-Ala.), who had been counted on to provide the 60th vote if a 59th could be found. Sources said yesterday that Sparkman's vote is now uncertain.

There was talk of major concessions to pick up wavering senators, but labor lobbyists reportedly objected strongly, and the question was shelved at least until Monday. One widely discussed concession involves dropping a provision that would expand union access to company property during organizing drives.

"The problem is that you can't find a senator who is guaranteed to be won over by a single concession," at least one that would be palatable to organized labor, said one source.

The legislation, which passed the House easily last year and then ran into a massive opposition campaign from business this year, would set deadlines for union representation elections and impose stiff penalties on employers who violate the law in trying to thwart unionizing and bargaining efforts. It is organized labor's top goal for this session of Congress.