WASHINGTON (AP) _ The Congressional Budget Office is preparing to issue a report increasing surplus projections only slightly, The Washington Post reported.

The paper quoted CBS director June E. O'Neill in today's editions as saying that although surplus estimates may be revised up by an average of $15 billion a year, ``I wouldn't think there would be a sea change beyond what we've already announced.''

Last month, the congressional agency revised its economic forecasts and predicted a surplus in the range of $43 billion to $63 billion this year, followed by $39 billion in fiscal 1999 and nearly $80 billion by 2002.

In an update to be given to Congress shortly after it returns from its Fourth of July recess, the CBO is likely to keep its current estimate for this year but peg future surpluses in the neighborhood of $49 billion in 1999, $36 billion in 2000, $43 billion in 2001 and $92 billion in 2002, the Post said. ``Technical corrections'' could move those figures upward or downward, unidentified CBO officials told the newspaper.

The relatively small increase would be a blow to hopes by Congress' Republican leadership to finance as much as $100 billion of tax cuts without having to cut politically popular programs.