The Los Angeles County Metropolitan Transportation Authority broke ground Friday on the second phase of construction on the Purple Line subway down Wilshire Boulevard, a project decades in the making that will transform transit on the busiest corridor in the city.

The 2.6-mile section will extend from La Cienega Boulevard into downtown Beverly Hills and Century City, adding two new stations in those locations at a cost of $2.53 billion.

Officials have promised the full nine-mile subway to Westwood will be completed by 2026, before the city hosts the Olympics in 2028. The University of California, Los Angeles in Westwood will be the Olympic Village, and the subway will be a central connection during the event.

To achieve this, Metro must accelerate its timeline by 10 years, undertaking construction of the final section to Westwood simultaneously with sections started earlier.

But issues with federal funding for the third section of the Purple Line have called the aggressive schedule into question.

Half of the first two sections have been funded by Measure R, the half-cent sales sales tax approved by county voters in 2008, and half through federal matching grants.

The final section to Wilshire received extra funding from Measure M, the sales tax increase approved by voters in 2016, to accelerate the project timeline. The budget and timeline assumed continuation of federal matching grants.

The Federal Transit Administration had already evaluated the Purple Line Phase Three and deemed it worthy of receiving funds — a grant agreement for about $1.3 billion projected for 2018.

But that was thrown into doubt last year when President Trump proposed cutting the Capital Investment Program, which funds major transit projects, including the Purple Line. He similarly proposed cutting the transit funds in 2019, even as he proposes an infrastructure investment package.

Earlier this month, though, Congress passed a two-year spending bill that could spell good news for Metro. The Senate recommended a funding level for the grant program that would cover the Purple Line Phase Three, but official appropriations have yet to be made and approved.

Metro spokesman Dave Sotero said the agency was "encouraged" by a budget deal that he said sets the stage for approval of transportation spending. He said Metro is hopeful the project will receive its grant by the end of the year.