WASHINGTON—Amtrak is planning to begin major repairs on the aging railroad tunnels beneath the Hudson River that link New Jersey and New York, with officials saying they can no longer wait for new tunnels to be built.

The railroad and the regional congressional delegations have pushed for years for the construction of a new two-track tunnel under the Hudson, which would eliminate a bottleneck in the Northeast Corridor and allow Amtrak to close existing passageways, known as the North River Tunnels, for extensive repairs.

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