The Senate agreed yesterday to start voting Tuesday on the natural gas compromise, but there may not be a final vote until a week from Wednesday.

In exchange for the stretched-out debate time, supporters won a guarantee there will be no endless filibuster, which they were not sure they could stop.

The multibillion-dollar gas bill falls between President Carter's plan to continue federal price controls at higher levels and the Senate vote to deregulate new gas in two years by providing for a phase-out of controls on new gas by 1985.

Tuesday afternoon the Senate will vote on a motion to send the bill back to a House-Senate conference with instructions to Senate conferees to insist on striking out the pricing provision that is the heart of the bill. This is supported by a coalition of pro-producer senators who want faster deregulation and pro-customer members who don't want it at all.

If that motion fails, other recommittal motions could be offered. If they all fail, the Senate would vote up or down on the conference report at 1 p.m. Sept 27. If approved, it would go back to the House for another final vote.

During this 12-day period the Senate may go on a two-track schedule, as if often does during filibusters, to act on other legislation for part of each day.

Earlier, supporters of the bill thought they could easily muster the 60 votes needed to stop a filibuster. But after Minority Leader Howard H. Baker Jr. (R-Tenn.) announced his opposition to the bill, they feared they might lose the legislation - which Congress has worked on for 16 months, and off and on for 25 years - to a filibuster. Senate leaders worked for most of this week for a time agreement, which they finally got late yesterday.

Majority Leader Robert C. Byrd (D-W.Va.) said that even though it appears neither side has a majority for its position now, it is the duty of the Senate to bring the gas bill to a vote. It is the major part of President Carter's top-priority energy bill with much chance of passage.

Although neither side has a majority from Senators who have decided or announced their position, supporters are ahead and gaining. During the last two days six liberal Democrats who had voted for continued regulation last fall announced their support of the compromise. They are Sens. Adali E. Stevenson (Ill.), Thomas F. Eagleton (Mo.), Thomas J. McIntyre (N.H.), Patrick J. Leahy (Vt.) and Iowa's John C. Culver and Dick Clark.

Most were won over by arguments that the bill would bring more gas into interstate markets where there have been shortages, that prices will go up with or without new legislation but that the bill would give residential consumers initial protection from price increases, and that the bill would strengthen the dollar abroad and show the world that this nation intends to cope with energy problems.

Sen. James Abourezk (D-S.D.), a pro-consumer opponent of the bill, convenced his Judiciary subcommittee yesterday to question Charles Curtis, Chairman of the Federal Energy Regulatory Commission, about problems in administering the complex legislation.

Curtis said the commission could administer the act but that it would need nearly 300 additional professional staff and other help that perliminary estimates put at a first year cost of about $20 million.