Google Fiber is pausing its expansion into new markets, losing its top executive and planning a round of layoffs. It is the clearest signal yet that the ambitious effort may be on life support.

Craig Barratt, the CEO of Access, the division that includes Fiber, announced the changes along with his decision to step down in a blog post late Tuesday.

"In the cities where we've launched or are under construction, our work will continue," Barratt said. But for additional cities that were in talks to receive Google Fiber, "we're going to pause our operations and offices while we refine our approaches."

Barratt also said Google Fiber will be "reducing our employee base." A source familiar with the matter said Google Fiber would cut 9% of staff, or more than 100 employees.

Jessica Reeves, a spokeswoman for Google Access, declined to comment on the layoffs.