The city’s rail project was thrown into further disarray Friday when Mayor Kirk Caldwell announced that he has notified the Federal Transit Administration of the city’s decision to withdraw from its “participation in the procurement” of a public-private partnership for the final leg of the city’s $9.2 billion rail project.

Caldwell said it’s up to the Honolulu Authority for Rapid Transportation to cancel the procurement of the so-called public private partnership, or P3 project, with an unidentified contractor.

Until it is canceled, the procurement remains active, which keeps the details of the proposals confidential.

“I remain committed to the rail project and encourage HART to explore a more open and effective approach of continuing the construction to Ala Moana,” Caldwell said in a statement. “I hope to see the timely development of an alternative bid strategy, such as a more traditional design- build approach, so this important transportation infrastructure project can continue to move forward.”

Caldwell’s statement threw the future of the state’s largest public works project into further uncertainty just one day after the HART board decided not to take action on a motion Thursday to tell its CEO and executive director, Andrew Robbins, that he will not be retained after his three-year contract expires Dec. 31. The deadline for the end of Robbins’ contract coincides with HART’s deadline to notify the Federal Transit Authority of its P3 plans.

Robbins is the city’s highest-paid employee, with an annual salary of $317,000, a $55,000 annual housing allowance and a $7,200-a-year transportation allowance, plus the possibilities of raises and bonuses.

Board members voted Thursday not to consider a second proposal to establish a search committee to find a replacement for Robbins.

What happens next for both Robbins and the future of the P3 is unclear.

Some HART members privately were stunned at Caldwell’s announcement and declined to comment.

Robbins said in a statement, “While the city has announced its withdrawal, I need to emphasize that HART is not canceling the procurement and is instead considering its options as to how best to now move forward with the construction of the City Center segment and completion of the project. HART is very disappointed in the city’s decision to withdraw.

“World class teams of developers and contractors stand ready to complete the project for the people of Honolulu. After nearly two years of detailed work on the current City Center procurement, HART does not consider it in the public interest to walk away at this point, especially since the Hawaii Procurement Code provides opportunities to achieve a successful contract award, as was pointed out yesterday to the HART Board of Directors by the State Procurement Officer.”

The procurement officer, Sarah Allen, did not respond to a request for comment.

Council member Kym Pine asked Caldwell, in a letter, to brief the City Council on the situation.

Former Mayor Mufi Hannemann, the project’s earliest booster, acknowledged that Caldwell’s announcement threw the project into disarray and likely will lead to further delays.

“They basically decided to cancel it,” Hannemann said. “The good news, from what Andy’s saying, is they’re going forward. HART is committed. That’s the wise thing to to do.”

“It’s certainly not dead,” Hannemann said. “The city cannot stop HART from continuing the process.”

HART is a semi-autonomous city agency.

But Hannemann acknowledged that HART officials are likely waiting to see what happens next.

“They’re probably waiting with bated breath,” he said.

With the HART board failing to follow through on its recommendation from its Human Resources Committee to let Robbins’ contract end and search for his successor, Hannemann said, “The perfect world … would be to see if he can finish it up. I want to see the process play out. What’s the alternative?”