White House and congressional budget negotiators said last night they were close to agreement on a plan to reduce the anticipated fiscal 1988 federal deficit by about $30 billion, and could tie up the loose ends as early as today.

Meeting throughout the day under increasing pressure to conclude a deal and send a positive signal to jittery world financial markets, negotiators emerged about 8:30 p.m. and cautiously said an accord is near, after more than three weeks of talks that have come close to agreements that soon fell apart.

"We're getting very close," said Sen. J. Bennett Johnston (D-La.). "We have to recheck the whole deal and see if it works. Everything could always come unraveled."

The framework for a possible accord was reached after legislative leaders and White House officials led by chief of staff Howard H. Baker Jr. and Treasury Secretary James A. Baker III abandoned any hopes of including any reductions in cost-of-living allowances (COLAs) for Social Security recipients and other federal retirees and workers.

But, by failing to find alternative savings for the $2 billion to $3 billion the COLA adjustments would have provided, the negotiators had to settle for a minimal deficit reduction framework that calls for fewer tax increases and reductions in spending from entitlement programs, those that automatically confer benefits to those who qualify.

One source close to the talks said that the current package, which could still undergo some change, calls for $9 billion in higher taxes rather than the $10 billion sought by many negotiators. In addition, instead of $5 billion in savings from entitlement programs, the negotiators have settled for $3.8 billion.

The entitlement savings come largely from reducing farm subsidies about $900 million, cutting Medicare by $2 billion and making $400 million worth of changes in federal salary grades.

Sen. Bob Packwood (R-Ore.), one of several lawmakers who had urged modest reductions in COLAs for federal workers and retirees, said he was "disappointed" with the final size and shape of the package.

"We missed a great opportunity to achieve something of grandeur," Packwood said. He said financial markets would find the $23 billion in across-the-board spending cuts that are legally mandated to occur Friday if no agreement is reached "more credible" than what negotiations have yielded after nearly four weeks.

Once onetime savings are subtracted from the package on the table last night, the resulting deficit reduction would be about the $23 billion in automatic cuts required by the revised Gramm-Rudman-Hollings balanced-budget law.

One Reagan administration participant said "this may not seem like a lot but it's probably the best we are able to get -- and we need an agreement."

Both congressional and White House negotiators are increasingly anxious to wrap up a deal in order to demonstrate U.S. financial leadership to still-volatile markets. James Baker repeatedly made that point in recent days.

The Dow Jones Industrial Average of 30 stocks fell 26.85 points yesterday.

Though there may be disappointment that longstanding political disagreements among the various parties resulted in a modest package, many involved in the talks said they believe even a minimal agreement is better than allowing the automatic cuts because it demonstrates the government is able to function in a crisis.

The package that may be approved today also includes cuts in defense spending of about $4.9 billion and reductions in discretionary domestic programs such as education and law enforcement of about $2.6 billion. Additional savings would come from user fees, enhanced tax collections, and savings on interest on the national debt. There would also be one-time savings of about $5 billion from refinancing rural electric loans.

One congressional aide close to the talks described it as "a terrible package" that may encounter significant opposition among Senate Republicans.

"You can't quite describe it as a tentative agreement," Packwood said last night, until "everybody comes back {today} and everything works . . . . {Treasury Secretary} Jim Baker could not say tonight, 'You bet.' "

But House Majority Leader Thomas S. Foley (D-Wash.) said the negotiations are now "so close I cannot imagine we would fail."

Nevertheless, Foley and others indicated that a tentative agreement would not occur until staff budget analysts can confirm that anticipated savings from specific policy decisions are accurate.

In addition, the negotiators must still settle the potentially troublesome issue of ensuring that about $45 billion in savings for fiscal 1989, which begins next October, can be locked in by legislation that binds the congressional committees that control federal spending. Negotiators are still not sure where all the projected 1989 savings will come from.