Let the bidding begin.

City officials yesterday began soliciting bids for the first leg of Honolulu's planned $5.3 billion, 20-mile rail transit system.

The contract, which has an estimated value of $550 million to $600 million excluding extras for contingencies, will cover the design and construction of the first 6.5 miles of elevated guideway from East Kapolei to Leeward Community College. It will be the biggest deal so far on what's expected to be Hawai'i's largest-ever public works project.

The procurement is part of a plan to launch limited train service in phases starting in late 2013 and ending in late 2018.

"It's obviously a big step in this project," City Council Chairman Todd Apo said. "It's a project that's going to bring some economic benefit to our island at a time when we need it so moving forward with it as soon as possible is really going to help our island get through these economic doldrums."

The contract is expected to be awarded after the federal government approves the project's environmental impact statement. City officials hope that will happen this fall so that construction can begin in December.

Contractors have until March 13 to respond to the request for proposals. The selection process will take about six months and then final negotiations will be undertaken with the proposer providing the best value to the city.

City officials had wanted to issue the request for proposals earlier. However, the process was delayed slightly because the City Council had to fix a glitch in the original law directing the city to go forward with the project. The council passed legislation fixing that problem last week.

Under current plans, the first construction deal will be a design and build contract, which means the team selected only will be responsible for designing and building the first six miles of elevated guideway. That deal will be followed by separate contracts for vehicles and systems and for a maintenance yard.

Currently, the city plans to operate the train system, though that can change between now and late 2013 when limited service is set to begin. Full service is scheduled to start by 2019.

"This is a significant milestone and a tremendous step forward," Mayor Mufi Hannemann said in a news release. "O'ahu's voters told us they wanted a rail system and we've taken that message to heart."