The White House yesterday took down the obituary notice for welfare "reform" that two senior presidential aides had posted on Tuesday and said it was a ghastly error.

"I have every hope and expectation that the welfare reform proposals will be passed by the Congress this year." President Carter said in a handwritten letter to Rep. James C. Corman (D-Calif.), chairman of a special House subcommittee handling the bill.

Corman had expressed dismay after The Washington Post, in Wednesday's editions, reported that two senior Carter aides in separate interviews said there was little chance the calendar would allow Senate action on welfare revision this year even if Corman was able to steer the bill through the House.

That judgement - though shared by many key legislators - was viewed as an inadvertent or intentional signal that the White House was softening its pressure for what had been called a high-priority part of the president's program.

Corman, Secretary of Health, Education and Welfare Joseph A. Califano Jr. and Sen. Daniel Patrick Moynihan (D-N.Y.), chairman of the Senate welfare subcommittee, met last night in Corman's office and said the bill could be considered by the Senate this year if passed by the House by April 1 - a deadline Corman said he could meet.

Earlier, House Speaker Thomas P. (Tip) O'Neil Jr. (D-Mass) told reporters that in the House "we intend to go forward," but added that it might be pointless to do so "if it's only the House that's going to pass the bill, with no hopes in the Senate."

Senate Majority Leader Robert C. Byrd (D-W. Va.) assessed the chances of favorable Senate action this year as being "reasonably fair."

White House press secretary Jody Powell said the presidential aides who spoke to The Post "were trying to indicate the difficulties" facing the proposal "and maybe they overdid it a bit."

Powell said the president "hopes to see it passed, but he is not laying odds on it."

Corman yesterday distributed copies of the president's letter to reporters as his special House subcommittee met to continue work on the massive welfare revision package. Denying that the president has dropped hopes for the bill for this year, Corman said he had been assured over the telephone by Moynihan that there will be "ample time" for the Senate to act if Corman shepherds the controversial measure through the House by April 1.

"Moynihan said he fully expects to get it to the Senate floor this year," Corman said.

Despite the president's letter, the bill faces strong opposition in both chambers, partly because of its high price tag and partly because influential members such as Ways and Means Committee Chairman Al Ullman (D-Ore.) and Senate Finance Committee Chairman Russell B. Long (D-la.) don't like its approach. The assessment by the two presidential advisers, that the bill can't pass the Senate this year, might be a realistic one.

Yesterday the Congressional Budget Office, in a new analysis of potential costs of the bill, put the net new cost in 1982, the first year the proposal would be fully effective, at $21 billion more than existing programs. That is the highest figure ever given by anbody.

The CBO said the total gross cost to the federal government if the bill went into effort with amendments added so far by Corman's subcommittee would be $48.9 billion.

However, CBO says the new program will replace $27 billion in existing programs, so the net new cost would be lower.

The administration using somewhat different methods of calculation, estimates that net added costs in 1982 with subcommittee changes would be about $11 billion. A major reason for the difference is that the administration's attributing higher costs to existing programs than is the CBO.

Ullman said outright at yesterday's meeting that he doesn't like the Carter bill and will offer a substitute at an appropriate time. Long has repeatedly made it clear he doesn't like the bill.

Rep. Guy Vander Jagt (R-Mich.), alluding to the strong opposition from many sources, suggested that despite Carter's letter, the story in The Post might be the administration's way of sending a signal to Congress that the welfare plan is now on a back burner. But Corman said, "I believe the President: I think he's serious about making every effort to get the bill out this year."

Presidential assistant Stuart Eizentat has been working with congressional supporters to help develop a compromise on a key issue holding up the bill - whether welfare clients steered to low-wage government "last resort" jobs under the new program should get paid the federal minimum wage or a higher local "prevailing wage" for the types of work done. Labor unions want the prevailing wage but the administration's orginal proposal called for the minimum wage.Several times a compromise has appeared important only to slip away.

The president's letter to Corman said "although it will not be easy, there is growing interest in the Senate" in passing the bill this year, and "we will do our best in cooperation with you, Sen. Mcynihan and others to be successful this year. Call on me directly when I can be of help, and of expected to play singles against the course, Secretary Califano, other members of the Cabinet and all who work with us are eager to be continuing partners with you."