The House Energy and Commerce Committee, working on a tight schedule to complete a Superfund bill, reversed itself yesterday and agreed to put deadlines on toxic-waste cleanups by the Environmental Protection Agency.

In the Senate, efforts to move Superfund legislation appeared to be picking up momentum after weeks of inaction. After a meeting with Senate Majority Leader Robert J. Dole (R-Kan.) and administration officials, Environment and Public Works Committee Chairman Robert T. Stafford (R-Vt.) said he had a "reasonable expectation" that the measure would be put to a floor vote before Congress recesses in August.

Dole had earlier received a letter signed by 64 senators, warning that funds for the toxic-waste cleanup program will run out at the end of September and that delaying action could jeopardize hundreds of cleanups.

"That means there are 66 senators in favor of this action," said Stafford. Neither Stafford nor Senate Finance Committee Chairman Bob Packwood (R-Ore.) signed the letter, but both have cleared the bill through their committees and have pushed for early consideration.

Disputes among Democrats have slowed House action on Superfund, but the Energy and Commerce panel took several major steps toward resolving the conflicts yesterday.

The committee approved by voice vote an amendment that would require the EPA to start 540 cleanups within six years or give Congress a detailed explanation of why the cleanups could not proceed.

A day earlier, the panel had rejected a similar amendment that would have required the agency to start 600 cleanups within five years.

Rep. Ron Wyden (D-Ore.), who sponsored the compromise language, said the schedule would "hold the EPA's feet to the fire" without reducing the agency's flexibility to deal with complex chemical sites.

Rep. James J. Florio (D-N.J.), who has led the battle to impose deadlines on Superfund cleanups, said he was pleased with the compromise. "The end result is essentially almost the bill we tried to get out," he said.

In a session that contrasted sharply with the bitter intraparty wrangling that so far has characterized Superfund's march through the House, the panel also adopted an amendment that would restore states' rights to sue for damages to natural resources caused by federal facilities. The provision is part of the current Superfund law but was stripped from the bill this year in what Rep. Timothy E. Wirth (D-Colo.) called "an enormous abridgment of states' rights to protect themselves."

The committee also rejected, by a lopsided vote of 33 to 8, an effort to trim $1 billion from the $10 billion, five-year bill by reducing federal contributions to the fund.

Rep. Howard C. Nielson (R-Utah) had proposed the cut, citing federal deficits and the administration's desire for a leaner bill. At $10 billion, the House version is almost twice the size of the $5.3 billion program supported by the Reagan administration.

The Senate version, at $7.5 billion, is also larger than the administration wants, but Stafford said yesterday that the administration appears less concerned about the size of the program than the source of the taxes that will fund it.

The Senate Finance Committee has approved a broad-based corporate tax to expand the size of Superfund, which is now funded largely by an excise tax on chemical feedstocks. Treasury and White House officials have strongly opposed the broader corporate tax, arguing that it is an open-ended invitation to higher federal spending.

Stafford said Dole had agreed to help resolve differences between Packwood and the White House, but he said that floor action will not depend on the outcome of those negotiations.

"We can make a persuasive case for passing this bill," he said, adding that he would prefer to pass Superfund as it is and negotiate taxing mechanisms with the House "if we're faced with a veto."