He tweeted about the rally this Saturday, saying that next week "I will be holding a BIG rally in Pennsylvania".
The president announced around this time that he wouldn't be attending this year's White House Correspondence Dinner.
Further details about the event have yet to be revealed.
U.S. president Donald Trump has pledged to mark his 100th day in office with a "BIG" rally in Pennsylvania.
Trump on Saturday also said he plans to announce new tax reforms next week.
Sanders urges Democrats to reach out to Trump supporters
Sanders - a claim the senator made repeatedly during the primaries. "That offended people when they went to vote". Some in the crowd also booed the first mention of the Democratic National Committee.
Trump himself talked repeatedly about his first 100 days when he was campaigning previous year.
Mr. Glassner said the rally, which will be the fourth in recent weeks, will review Mr. Trump's accomplishments since taking office in January.
And on the biggest stage of all, as he accepted his party's nomination at the Republican National Convention in Cleveland, Ohio, he promised to ask every government department to provide a list of wasteful projects for him to eliminate in his first 100 days.
His absence from the dinner and the decision by top White House officials to shun the event in solidarity with the president has put a damper on the affair next Saturday. "Looking forward to seeing our bravest and greatest Americans!" he tweeted.