The announcement came a day after Amtrak said it couldn't guarantee the tunnels would be restored before mid-January.
On Monday, "Amtrak's position was No. 1, not to share their position, and No. 2, when they did share their position they said sometime in late January," Rep. Steve Israel (D-Huntington) said during a news conference at the Hicksville LIRR station. "What changed is [LIRR Commuter's Council chairman] Mark Epstein called me and said we need to put more pressure on Amtrak. We publicly called on Amtrak to be more transparent and abide by a deadline, and the CEO of Amtrak apparently heard us."
"We understand the importance of restoring full LIRR service and are committed to doing so by the Christmas holiday," Boardman said in a statement. "We appreciate the continued cooperation from LIRR and are diligently working to make the needed repairs."
Israel said he asked Boardman to provide a written statement to LIRR president Helena Williams detailing the guarantees. "We are heading into the busiest travel season," Israel said. "We do not want Christmas chaos."
Williams called the change "good news" and said in a statement: "We look forward to receiving a detailed installation plan from Amtrak to confirm exactly when each tunnel's signal system will be restored to full service."
Amtrak owns and operates the four East River tunnels, two of which have been out of service since being damaged by flooding during superstorm Sandy. On Monday, Williams said she wanted Amtrak to complete its repairs in the tunnels by the end of the year to avoid train cancellations and heavy crowding into 2013.
Epstein, speaking with Israel at Tuesday's news conference, called on Amtrak to provide LIRR riders with "regular updates on progress being made" on the repairs and "any work schedule changes."
Amtrak has installed a temporary signal system inside the two damaged tunnels while it awaits completion of repairs of several complex signal cases that were destroyed by the corrosive floodwaters. Until the signal system is fully restored, the LIRR can run only about 70 percent of trains during the morning and evening rush hours.
Williams said she was anxious to have Amtrak fix the problem, which has led to heavy crowding on LIRR trains.
"We want to start the new year giving customers back the full train schedule," Williams said. "We are certainly not in control of our own destiny, but we are very strong advocates."
With Alfonso A. Castillo