The decision by union leaders to extend their consultation period over a deal reached with the city at the weekend, has escalated a political battle with Chicago's mayor. Rahm Emanuel vowed to end what he called an illegal strike. It's the first of its kind in 25 years, and is awkward for President Obama, who has close ties to the mayor and whose political career was forged in Chicago. In a tough election battle, he needs the support of the teachers unions, the Democrats have long counted on. But the president has pushed for the very reforms at issue here, including teacher evaluations the union says could lead to thousands being unfairly sacked.