Senate budget conferees are considering a plan to impose an oil-import fee and delay inflation adjustments for income taxes and major benefits programs such as Social Security as part of a $340 billion, three-year compromise offer to the House on deficit reduction, sources said last night.

A majority of the Senate conferees were reported to favor the plan, one of several under consideration, to break a week-long impasse in budget negotiations between the chambers, even though the tax provisions appear to fly in the face of President Reagan's opposition to increasing taxes to reduce budget deficits.

Administration officials, however, appeared to carefully qualify their opposition to increased taxes yesterday, particularly with respect to oil-import fees.

The plans will be discussed today in a meeting between the conferees and Senate Budget Committee Chairman Pete V. Domenici (R-N.M.), who also is chairman of the House-Senate budget conference.

Domenici, questioned by reporters as he awaited a meeting with Senate Majority Leader Robert J. Dole (R-Kan.) on strategy for the budget talks, said last night that no decisions had been made, although he described the conferees' proposal as a "good plan . . . a good approach."

Dole previously floated the idea of a delay in inflation adjustments and has spoken favorably of an oil-import fee, but he declined to say whether he endorsed the plan as an offer in the negotiations. "We'll have to see," he said.

A source close to the negotiations said that the Senate proposal would impose a $5-a-barrel fee on oil imports and adjust both tax rates and benefits programs every two years, rather than annually as is now done. The plan also would modify some of the Senate's proposed domestic spending cuts to come closer to House demands.

Over three years, the oil-import fee would yield $20 billion to $30 billion; the inflation adjustment delay would bring in $19 billion. Still to be determined are domestic spending cuts, a source said.

The $340 billion, three-year savings is $45 billion more than the Senate anticipated in its version of the budget and about $80 billion more than the House approved.

Another plan under study would save about $290 billion through spending cuts alone.

In response to questions about an oil-import fee earlier in the day, White House spokesman Larry Speakes declined to comment on whether such a fee would be ruled out under Reagan's condition that no new taxes be imposed as a means of deficit reduction.

But a senior White House official who was familiar with the efforts to obtain a compromise said that an oil-import fee "would not necessarily be considered a new tax."

Yesterday, before the Senate conferees plan emerged, Reagan exchanged exhortations with congressional leaders about the need for a budget compromise in the next 10 days, although after the meeting some White House officials expressed pessimism.

Dole said he hoped the Senate would have an offer to make to the House by Friday, and House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) indicated, as he has before, that the House can "stretch . . . a little" its offer for domestic spending cuts.

An atmosphere of stalemate has persisted for a week since House-Senate negotiations on deficit reductions broke down in acrimony a week ago. The key figure has been Dole, who has expressed frustration that options that might satisfy the House fall short of minimal Senate demands. He has spoken of "new approaches" such as the every-other-year inflation adjustments for taxes and benefits programs.

"I haven't given up hope for a meaningful package," Dole said after the White House meeting.

Speakes said Reagan stressed the importance of getting a budget settlement before a month-long congressional recess starts Aug. 2.

"Every village, every town, every municipality, every state has a budget, yet the greatest economic entity in the world does not have a budget," Speakes quoted Reagan as saying. "How can the country go forward without a plan?"

Speakes said that no one disagreed with the president, but no one presented a compromise.

As the meeting ended, Speakes said O'Neill shook hands with Reagan and said, "Mr. President, you look good." "I'll feel better when I get a budget," responded the robe-clad president, recuperating from July 13 cancer surgery.

Meanwhile, on a largely party-line vote of 242 to 184, the House approved a resolution aimed at forcing appropriations bills to come in under targets set by the House-approved budget, even if a compromise is not reached.

"The House is firmly committed to achieving at least $56 billion in deficit reductions this year, and this message can never to delivered too strongly to the Senate or to the American people," said House Budget Committee Chairman William H. Gray III (D-Pa.).

But Republicans called the resolution meaningless. "Do we really believe the public is so gullible that we can simply pass a resolution which says that the Congress has adopted a piece of major legislation when as a matter of public record we haven't?" said Rep. Silvio O. Conte (R-Mass.). He said the move was the "ultimate congressional junket to political Disneyland."