It’s off the rails.

Amtrak will push back the start of its three-year East River Tunnel closures by two weeks after Mayor Eric Adams, Gov. Kathy Hochul and other pols blasted the shutdown as potentially leaving millions in commuting hell.

The East River Tunnel Rehabilitation project will tentatively get underway on May 23 instead of this Friday, Amtrak President Roger Harris revealed in a letter to Hochul Tuesday.

The two-week delay comes after the MTA informed Amtrak that a key infrastructure project managed by the Big Apple agency is, once again, behind schedule.

The train company signaled it would use the extra time to modify its much-hated service plan — that was approved by the MTA — and could risk train delays for millions of riders.

“We believe it is important to present a united front to the traveling public,” Harris wrote.

Harris said that the Long Island Rail Road’s East-Bound Reroute (EBRR) project, managed by the MTA, is already six months late and will not be completed in time for Amtrak’s initial planned closure that was set for Friday.

“In light of this delay, and the concerns you and other stakeholders raised regarding the service plans, we are working with our partners at MTA and NJ TRANSIT to move the start of construction by two weeks to May 23,” Harris wrote.

The MTA took offense to Harris’ characterization in a statement to The Post late Tuesday.

“The fundamental issue is that Amtrak has consistently refused to consider the approach to rebuilding the tunnels that the MTA and others have recommended for years,” a spokesperson said.

“When LIRR met with them in recent weeks, it was clear that Amtrak was unprepared for this work and unready to begin, and all of our concerns were reinforced. That’s why it’s even more concerning that they are now looking to shift blame to others.”

Once the project does kick off, Amtrak will close for repair one of the four East River tunnels that connects Manhattan’s Penn Station to Queens, forcing the MTA, Amtrak and New Jersey Transit to use fewer tracks during the construction.

Workers are expected to alternate which tunnel to fix up during the three-year project – a plan that has commuters worried and outraged.

Harris requested a meeting with Hochul, and officials from the LIRR and Metro-North Railroad to discuss options such as rerouting service to Grand Central Terminal — a solution Hochul had proposed in a previous letter.

While Harris stood by the need to fully close a single tunnel tube at a time – which Amtrak maintains is the only safe and effective way to repair damage from Superstorm Sandy in 2012 – he said he hopes the meeting would identify blind spots in the service plan.

“Any other solution would be an expensive, short-term band-aid and a disservice to passengers and taxpayers,” Harris claimed.

Amtrak said it is now working with the MTA and New Jersey Transit to adjust service plans and use the additional time to explore mitigation strategies aimed at minimizing disruption.\

He also wrote that it’s important that all the agencies involved show they are “good stewards of this significant taxpayer investment.”

Earlier Tuesday, Adams sent a letter to US Transportation Secretary Sean Duffy asking him to intervene and force Amtrak to close the tunnel only on nights and weekends — even though it could make the $1.6 billion project cost more.

“Amtrak has refused to listen to reason,” Adams charged, arguing shutting down the route completely “makes no sense whatsoever.”

“Instead of doing the logical, least disruptive thing — keeping one tunnel open during the day, including rush hours, and doing repairs over time, at night and on weekends — Amtrak has decided to close that one tunnel and start repairs from scratch, immediately causing significant service limitations and potentially jeopardizing train service altogether,” Adams said in his letter.

A slew of other elected officials, including Nassau County Executive Bruce Blakeman and US Rep. Michael Lawler, have slammed the planned closures.