Construction is just about finished on an underground tunnel connecting the R train at Cortlandt Street with the eight lines that run through the Fulton Street subway hub, but straphangers will have to wait years to even set foot inside.

The Metropolitan Transportation Authority is planning to keep the tunnel -- known as the Dey Street Concourse -- closed until One World Trade Center and Four World Trade Center open for business.

The $200 million walkway will offer riders a free transfer between Cortlandt Street and the Fulton Center.

Transit officials initially said it would be open next month, but will now likely remain blocked off until at least 2015.

The agency says it would be too expensive to maintain the passage until the buildings open because only a handful of riders will use it.