"Teachers have voted overwhelmingly to strike, should contract negotiations fail as CPS and the mayor does not reverse the hostile climate against us," said Lewis.
Chicago schools CEO Jean-Claude Brizard confirmed talks are still under way.
"It's unfortunate, honestly, that the CTU would be talking about a strike when we have so much work we have to do," said Brizard.
"Nobody wants to strike, right?" said Lewis. "Nobody wants that, but we are not going to be unprepared for it."
Cynthia Smith, who has been a CPS teacher for 25 years, works at Lane Tech High School and says 92.6 percent of the teachers at the school voted to strike if necessary in their mock straw poll.
"We think, first of all, about the kids," said Smith. "Secondly, about adequate resources in the schools, good work conditions, and fair pay."
Mayor Rahm Emanuel wants all elementary schools to go to longer school days. The teachers union is negotiating that issue as well as others, including a new contract.
"Next year, all schools move to longer school days and longer school year without any commitment from the district to give students and teachers the resources they need," Lewis said. "The school district, however, calls these experiments 'reform.'"
Mayor Emanuel reacted saying, "Don't take away from your main mission. Your job, what the people of the city of Chicago, the parents, the taxpayers expect of you, which is to teach our children. Any time away from that is time away from our children. And remember, what you're here for is to teach our children."
CTU president Lewis says the negotiations themselves are quite positive because they have a 35-member bargaining team with the city and that has never happened before in the past. However, they feel they need to be prepared to strike if necessary.