The Senate yesterday held the line against efforts to reshape its balanced-budget legislation as the White House denounced an alternative plan approved last week by the Democratic-controlled House.

The Senate's action, coupled with the White House offensive against the House plan, appeared to strengthen the administration's hand for the next round of House-Senate negotiations to resolve differences between the versions.

But it also made a compromise more difficult to achieve as the two chambers attempt to reconcile their plans before the Nov. 14 deadline for passage of a debt-ceiling extension, which has been tied to the balanced-budget legislation.

Earlier in the day, House Majority Leader James C. Wright Jr. (D-Tex.) said there was "ample opportunity for accommodation," but Senate Majority Leader Robert J. Dole (R-Kan.) said he was "not sure" there was much bargaining room.

While the White House reaffirmed President Reagan's support for the Senate bill, its criticism of the House version raised the possibility of a veto if an eventual compromise is tilted too far toward House provisions, especially those aimed at cutting defense spending.

Asked if Reagan would veto legislation along lines that the House passed, presidential spokesman Larry Speakes said the president "would have to look long and hard at a bill that would distort the original intent" of the Senate legislation, which Speakes said was to "apply budget reductions in a fair, across-the-board manner."

The House measure is "aimed more at political gain than deficit reduction," Speakes said.

The Senate bill -- sponsored by Sens. Phil Gramm (R-Tex.), Warren B. Rudman (R-N.H.) and Ernest F. Hollings (D-S.C.) -- would set fixed targets to reduce deficits from $180 billion to zero by fiscal 1991 and would require automatic cuts in most programs to meet the goals if Congress failed to do so.

The House alternative follows a similar formula but would speed up the process and require heavier cuts in defense, starting this year. It also would achieve a balanced budget in fiscal 1990.

In initial votes yesterday on proposed modifications in its original plan, the Senate rejected several proposals aimed at bringing it more in line with the House plan.

By 54 to 44, it killed a proposal from Sen. Lawton Chiles (D-Fla.) to protect the basic Medicare program from automatic cutbacks by putting it in a category that would expose it only to a spending freeze.

Then it voted, 55 to 43, against a proposal from Sen. Donald W. Riegle Jr. (D-Mich.) to lower the deficit ceiling for this fiscal year from $180 billion to $172 billion to assure that spending cutbacks start immediately. The House approved a ceiling of $161 billion, complaining that the Senate opted for an easy first-year target to protect Republicans seeking reelection next fall.

The Senate also rejected, 52 to 44, a Riegle proposal to protect veterans' programs from heavy spending cuts.

Senate Democrats might not even bring up the House plan for a vote. Republican leaders have expressed confidence that they have enough votes to reject it and pass a modified version of the Gramm-Rudman-Hollings measure. In yesterday's votes, moderate-to-liberal Republicans supported the Democratic-sponsored amendments, but their switch was offset by conservative Democratic support for the GOP position.

In debate over the Democratic proposals, Sen. Bob Packwood (R-Ore.), chairman of the first House-Senate conference on the budget measure, pleaded with the Senate to hold firm in order to strengthen its hand in a second conference, expected to start this week. "I beg the Senate to give us the strongest hand possible . . . ," he said.

In connection with the deficit target for this fiscal year, Senate Budget Committee Chairman Pete V. Domenici (R-N.M.) contended that a spending cut of $9 billion to $12 billion would be required even without any change in the ceiling.

Senate support for the Gramm-Rudman-Hollings proposal held firm despite signs of skepticism, even within Republican leadership ranks, about whether a compromise can be worked out and, if one is reached, whether the plan would work as intended.

Dole expressed reservations along these lines at a breakfast meeting with reporters, saying Congress has demonstrated in the last month that "we can't come together on a meaningful statute and, even if we did, we could change it, postpone it, modify it, repeal it, whatever."

In all, he said, "the one positive feature of the whole exercise" may have been to make a "pretty good case" for passage of a constitutional amendment to balance the budget, which could not be changed by legislative action, he noted.

But Dole did not back off his support for the Gramm-Rudman-Hollings plan.

"If we could finally come together with a reasonable approach to force us to take certain steps, that would be a good idea, as far as I'm concerned," he said. Moreover, he added, Congress probably cannot pass a debt-ceiling extension without it.

If an extension is not passed by Nov. 14, the government will exhaust its line of credit and run out of money to continue operations, according to the Treasury Department.