One of the leaders of the efforts to continue the current tax benefits for Individual Retirement Accounts announced last night he would not take his battle to the Senate floor, increasing the chances the historic tax-overhaul package will pass the Senate largely intact.

Sen. William V. Roth Jr. (R-Del.), who had sought to preserve IRA deductions in exchange for increasing taxes on groups ranging from cigarette makers to holders of municipal bonds, switched strategy last night. He introduced a resolution simply calling on a House-Senate conference committee to restore the IRA benefits to the bill. If, as is expected, the Senate passes a tax-overhaul bill, the conference committee will be in charge of reconciling the differences between that measure and the version of tax revision passed by the House.

Senate Majority Leader Robert J. Dole and Finance Committee Chairman Bob Packwood (R-Ore.), both of whom had pushed a strategy of no amendments, joined Roth in the resolution. But sponsors of other efforts to preserve IRAs, still considered the bigggest threat to passage of an overall tax package, said yesterday they plan to proceed.

The Roth action came on a day of stepped-up appeals to senators by the White House and Republican leaders to refrain from attempts to amend the package for fear that one amendment would open the floodgates to numerous others that could sink the bill.

Trying to head off another amendment, this one denying tax benefits to institutions involved in abortions, President Reagan told Republican senators at a morning meeting that he opposed the antiabortion amendment. While he opposes abortion, Reagan told the senators that the issue should be addressed outside the context of tax overhaul, according to White House spokesman Larry Speakes.

Sen. Gordon J. Humphrey (R-N.H.) said in an interview that he and Sens. William L. Armstrong (R-Colo.) and Jesse Helms (R-N.C.) nonetheless would offer an amendment this week to repeal the tax-exempt status of nonprofit hospitals, clinics and foundations that perform or finance abortions.

"It's a matter of principle," Humphrey said. "Do we subsidize abortion or do we not?"

The emotion-laden abortion amendment is seen by some senators as a potential threat to the bill. But Packwood said last night that he is certain he could muster the votes to defeat it.

Before Roth switched gears, he and other supporters of IRAs were floating three possible amendments to preserve benefits for all contributors to the tax-deferred accounts. However, Sen. Lloyd Bentsen (D-Tex.) said Democrats were split during a luncheon session on how to raise an estimated $14.7 billion to $26 billion needed to finance the change over five years.

Republicans were also said to be divided, particularly over Roth's approach. That lack of support, sources said, was one reason he decided to switch his focus to the later conference.

Aides to Sen. Max Baucus (D-Mont.) said he planned to introduce an amendment creating a 15 percent tax credit for all IRA contributions, financed by denying $310 of itemized deductions to each IRA holder. A bipartisan coalition of 11 senators, led by Alfonse M. D'Amato (R-N.Y.), also proposed a 15 percent tax credit, but planned to finance it by increasing the minimum tax on corporations and wealthy individuals.

The Roth resolution calls on Senate members of the conference committee to give "highest priority to retaining maximum possible tax benefits" for IRAs, without skewing the benefits of tax overhaul toward wealthy Americans.The resolution is to come to a vote today.

An estimated 30 to 40 amendments had been floated, but by day's end, no amendments had been brought to the floor by sponsors, prompting Dole to chide senators: "It's discouraging when you're watching C-Span and all you see is the Senate conducting a quorum call. We told people this would be exciting."

Also yesterday, Sen. Carl Levin (D-Mich.) released data from the Joint Committee on Taxation indicating that up to a third of taxpayers earning $30,000 to $40,000 a year would pay more taxes under the Finance Committee bill. Committee chief of staff David H. Brockway said in a letter to Levin, however, that the figures "suffer from flaws that are sufficiently serious that we are unwilling to stand behind them as a statistically valid projection."

Levin said he considered the figures a serious problem. "If these figures are unreliable, we've got nothing on which to base an assessment of how many folks are paying more and how many will be paying less," he said.