Updated at 4:08 p.m.

Some Chicago city employees will be laid off and hours at libraries will be shortened. That’s the early read on Mayor Rahm Emanuel’s first budget proposal.

Emanuel will explain how he plans to close a more than $600-million budget hole when he releases his plan Wednesday.

The mayor’s office briefed aldermen on some parts of the plan in meetings on Tuesday and asked them not to talk to reporters ahead of Emanuel’s formal announcement.

But sources who asked to remain anonymous said the plan includes a shortening of the hours at libraries across the city. Without directly confirming that cut, Emanuel defended it Tuesday morning by pointing out that things could be worse.

“[New York City] Mayor Bloomberg - who I have a lot of respect for - they closed libraries,” Emanuel told reporters at an unrelated press conference.

The mayor was more direct when asked about job cuts.

“I’m going to continue to make layoffs as we try to achieve our objective, to balance the 2012 budget, which we will do,” Emanuel said.

Emanuel has promised not to raise sales or property taxes to balance city hall’s budget, but new revenue is expected.

Ald. Joe Moreno, appearing on WBEZ’s Eight Forty-Eight, suggested putting a tax on billboards. On the same program, Ald. Michelle Smith advocated for increasing fees that businesses pay to reserve loading zones, which sources confirm is included in the mayor’s proposal.

Also expected, according to a source: a $15 city sticker increase for owners of sport utility vehicles.