Gov. Bob McDonnell (R) wants to nix a union deal for contractors for the Silver Line. (AP Photo/Daily News-Record, Nikki Fox)

McDonnell (R) has voiced a series of complaints about the new Silver Line project — including cost and management issues -- but wrote Monday that if a union-friendly deal for contractors is dropped the state’s contribution will be sent.

“If MWAA acts to ensure that this is the case, the Commonwealth will provide the $150 million in additional funding, without any further conditions, when it is due in 2013,’’ he wrote.

On Wednesday, the Metropolitan Washington Airports Authority, the quasi-public agency overseeing the $6 billion construction of Metro’s new Silver Line to Dulles Airport and further into Loudoun County, is expected to vote on whether to drop the labor incentive.

“The Commonwealth remains committed to providing its funding; however, certain legal issues must be resolved before this can occur,’’ McDonnell wrote in the letter.

In the spring, the General Assembly enacted a law and included language in the state budget that prohibit project labor agreements on the Silver Line project.

Loudoun supervisors have also said they won’t make an estimated $200 million contribution if the labor agreement goes forward.

Project labor agreements (PLA) typically ensure certain wages and working conditions while barring strikes and providing managers with flexibility in making work assignments. Such pacts are common in state and federal projects, and a voluntary PLA has been in place for the first phase of the Silver Line construction.

That phase, which runs through Tysons Corner to Wiehle Avenue, is expected to be finished in August 2013, about $150 million over budget. Planners wanted to have bids out in early March to pick a contractor for Phase 2 but now say they are at a standstill until Virginia and the MWAA board work out a deal.