Netanyahu promised Gantz last week that the swearing in would take place by Wednesday, but they decided to use US Secretary of State Mike Pompeo's visit to Israel on Wednesday as an excuse to take an extra day to settle disputes on the way to building a coalition.
Pompeo's visit was planned well before it was known that Netanyahu and Gantz would try to swear in their government on Wednesday.
Netanyahu has until May 21 at 8 p.m. to form a government, and if he fails Israel will go to another election in August.