Talks are planned for this week to keep the Metro to Dulles project on track.
The first phase of the Silver Line is expected to be completed by August 2013.
But the second phase, from Reston to Dulles Airport, may be derailed by financing issues related to politics and union issues. Virginia lawmakers don't want to contribute $150 million because the airports authority decided to give an incentive to bidders who use union labor.
The labor issue is also considered a deal breaker for officials in Loudoun County, Va. A new Board of Supervisors was elected last year and has talked of pulling out of the project to save money.
Transportation Secretary Ray LaHood called a meeting for Wednesday to try to reach an agreement on funding the project.
All the major stakeholders are expected to participate.