The schedule change comes as Sanders has barnstormed California, not leaving the state in more than a week. Meanwhile, a recent poll found the race closing significantly. Clinton's lead over Sanders had narrowed to just two points.
Details are scarce, but Clinton now plans to hold events in California from Thursday until the day before the state's June 7 primary.
Although she probably will secure enough delegates to clinch the nomination before polls close in California that day, a loss in the nation's most populous state would be an embarrassing end to the contentious Democratic primary.
Sanders has poured virtually all the resources that remain in his campaign into the effort to win California. There are 475 pledged delegates at stake there, and Sanders has said that his goal is to secure as many of them as possible to make the case at the Democratic convention in Philadelphia that he would be the stronger general-election candidate.