The Bloomberg administration announced Wednesday it had selected a Portland, Ore., company to run an ambitious bike-share program in New York City, but don’t break out the spandex cycling shorts just yet.

Amid unease about exactly how the city will integrate 600 rental stations and 10,000 bicycles into the crowded streets and sidewalks of New York, the official rollout date of the program has been pushed back until the summer of 2012.

Many other kinks and details are still to be worked out, like the pricing structure and the exact locations of the rental stations. Also missing are the requisite major sponsors to help defray the cost of the program. But when fully implemented, the program would become the largest bike-share effort in the country.

The selection of Alta Bicycle Share was announced at a news conference at a pedestrian plaza in the Flatiron district, where a sample bike station — a kiosk and a rack of sturdy, utilitarian bicycles — was on display.