Livni, the former Israeli Foreign Affairs Minister, made the announcement on Monday evening a few hours before the polling stations opened on Tuesday across Israel.
Some 5,880,000 eligible voters have started heading to the polls to cast their ballots to determine the future direction of their country.
The incumbent prime minister's Likud party slammed leftist leaders Herzog and Livni for this move in a statement following the announcement.
"Tzipi [Livni] and Boujie [Isaac Herzog's] wavering is a cynical move that is meant to increase the gap between the Zionist Union party and the Likud which would ensure an extreme left-wing government with the cooperation of the Joint Arab List and the parties on the left," Likud said in the statement as quoted by Jerusalem Post.
"As they surrendered with this move in response the polls, so they will surrender to international pressure and they will make concessions and retreat," Likud said.
According to the latest opinion polls, the prime minister's party has a good chance of losing the elections to the center-left Zionist Union. Exit polls will be announced Tuesday night on television, according to local media.