Senate supporters of the Carter administration's minimum wage proposals retreated yesterday for lack of votes and offered a compromise amendment on the hourly wage base even before the legislation could come to a vote on the floor.

The amendment, offered by Sens. Harris A. Williams (D-N.J.) and Jacob K. Javits (R-N.Y.), removed a key obstacle to adoption of the minimum wage bill that was approved a week ago by the Senate Human Resources Committee.

Williams said there was "considerable sentiment" in the Senate against an administration-backed indexing formula, under which the wage floor would have been set at 52 per cent of average manufacturing wages in 1979, and 53 per cent thereafter. The minimum wage, as a result, would have risen to $3.37 in 1981.

The House last week rejected that formula, substituting automatic increases in which the base would rise 75 cents in three steps, to $3.05 in 1980.

The proposed Senate amendment offers $1.10 in hourly minimum wage increases over four years, raising the base to $3.40 in January, 1981. Beginning in January, each annual increase is 25 cents.

Labor spokesmen reacted favorably to the William-Javits proposals, saying it represents an improvement over the House version.

"It flies very good with us. It offers more money and assures it over a longer period," said Albert J. Zack, spokesman for the AFL-CIO.

"With the House vote aginst indexing, they evidently felt they couldn't get it through," he said.

Another AFL-CIO official said that if the manufacturing wage indexing formula did not perish on the Senate floor, it would have become bottle-necked in House-Senate conference.

Williams said he had received "numerous expressions of concern" about the indexing provision, including complaints that it would make it difficult to alter minimum wage changes in the future.

"This (amendment) was put in recognition of that sentiment," an aide quoted Williams as saying.

Supporters of the amendment pointed out that under the plan, the 1981 minimum wage will be only about $400 less than the $7,429 poverty level projected by the Labor Department.

The four-year formula, Williams stressed, will provide security for at least that long for people at that income level.

The amendment would arise the current $2.30 hourly minimum wage to $2.65 on Jan. 1, 1978; to $2.90 on Jan. 1, 1979; to $3.15 on Jan. 1, 1980, and to $3.40 on Jan. 1, 1981.

Sponsors of the amendment are trying to get it to a floor vote next week, aides said.

Labor Secretary Ray Marshall endorsed the proposal, but issued a strongly worded attack on a provision of the minimum wage bill that would create a lower "subminimum," a longstanding Republican and business-backed idea.

He suggested that a subminimum might encourage employers to lay off low-income workers with families to support, in favor of hiring teenagers.

"Such action would accentuate rather than alleviate our unemployment problem," Marshall said.

Last week, the House, with a tiebreaker vote by Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.). defeated the youth subminimum proposal. It had been strongly opposed by the labor movement.