Microsoft has cut eight witnesses from its list of executives and business partners waiting to appear in anti-trust hearings.
The firm had planned to call 28 witnesses but will now call only 20. It said the move reflects its confidence it will resist nine states' call for stricter penalties.
Spokesman Jim Desler said the decision was made after assessing "what we believe are shortcomings in the states' case".
The states are pushing for sanctions to allow computer manufacturers make third-party software more prominent on the Windows desktop.
Microsoft's move means its only has eight witnesses left, including chief executive Mr Steve Ballmer.
One of those to go is vice-president Mr Richard Fade, who handles the firm's relationships with computer makers. In an interview with lawyers for the states, Mr Fade admitted computer makers were aggrieved at contracts drawn up after last year's settlement with the Department of Justice.
Mr Fade's omission from the witness list means his testimony will not now be considered by the judge.
Microsoft's move makes it possible the hearings, which began in mid-March, could end next week. But the states may call extra witnesses to rebut the firm's assertions.