Reservations for tickets to visit the 9/11 memorial will be available online starting tomorrow, an official said yesterday.

Visitors will be able to get timed passes to see the memorial — which won’t open to the public until Sept. 12, after events for victims’ families on the 10th anniversary a day earlier.

Memorial official Lynn Rasic told The Post that close to 4 million visitors would be expected in the first year.

Parts of the plaza that will be open in September will hold 1,500 people at a time, with no limit as to how much time one spends there.

Beginning at 9 a.m. tomorrow, ticketing will go live at 911memorial.org, Rasic said.

The memorial is to include two huge pools with 30-foot cascading waterfalls and the names of the 2,982 people killed in the attacks of Sept. 11, 2001.

The names of those killed in the Feb. 26, 1993, bombing of the World Trade Center will be inscribed on parapets around the waterfalls.