Senate Republicans offered yesterday to increase funding for poverty-related programs as part of an overall deficit-reduction compromise aimed at moving budget negotiations with House Democrats off dead-center.

But the senators continued to insist on freezing Social Security benefits for all but the poorest recipients and allowing defense spending authority to grow with inflation, agreeing only to a modest cutback in defense outlays for next year.

The offer from Senate Budget Committee Chairman Pete V. Domenici (R-N.M.) came at the end of a daylong bargaining conference, and there was no immediate response from Domenici's House counterpart, Rep. William H. Gray III (D-Pa.).

The proposed package was not expected to be acceptable to the House conferees, because of both the defense and Social Security provisions.

Senate Republicans had indicated earlier that the plan would be offered as a catalyst for serious bargaining, although Gray declared that he was anticipating a "public relations gimmick" as much as anything else.

In general, Domenici's plan would move toward the House's higher figures for poverty-related programs such as child nutrition, while continuing to demand the Senate's more restrictive figures for other domestic programs such as Amtrak and postal subsidies.

While insisting on eliminating cost-of-living increases for Social Security beneficiaries next year, Domenici agreed to add $2.1 billion in new spending to offset the effects of the freeze on low-income recipients.

"It still constitutes a violation of President Reagan's campaign promise" against tampering with Social Security benefits, said House Majority Leader James C. Wright Jr. (D-Tex.).

Regarding defense, Domenici said he would split the difference with the House on anticipated fiscal 1986 outlays, a largely cosmetic change that would not affect the Senate's original proposal to let defense spending authority grow with inflation.

The House, by contrast, has proposed a freeze in defense spending authority.

Spending authority -- total obligations spread over several years -- is the important Defense Department figure as opposed to outlays, which govern only what is spent in a particular year.

The Reagan administration originally asked for an increase of 6 percent in spending authority for defense after accounting for inflation and has indicated it will not compromise further.

Under Domenici's new plan, deficits would be reduced by $60 billion next year, slightly higher than the $56 billion approved earlier by the House and Senate. Over three years, it would cut deficits by $302 billion, compared with three-year totals of $259 billion from the House and $295 billion from the Senate.

The plan would produce a deficit of $167.6 billion next year, declining to $101.4 billion after three years, more or less in line with the goal of cutting deficits in half by fiscal 1988.

Domenici's offer came after more than a week of shadowboxing by the conferees that resulted in agreement on no major programs.

In offering the comprehensive compromise, Domenici said, "There is no other way to do it. There is no way we can resolve this piecemeal." Asked what would happen if it was rejected, he said, "We'll just have to wait and see."