A Port Authority vote on a $1.2 billion loan to finance construction of 3 World Trade Center was postponed until at least next month at a meeting Wednesday where agency commissioners debated the agreement.

Port Authority executive director Pat Foye told commissioners that the financial proposal would be a fair deal for the agency once a "small handful of open but significant items" are settled.

A revised plan is expected to be presented to the board for a vote in May, Foye told reporters after the meeting.

"We've made a great deal of progress -- we're not there yet," Foye said.

The deal to finance the building of 3 WTC is a renegotiation of a 2010 agreement between Port Authority and Silverstein Properties. So far, GroupM, a media company, is the only tenant that has signed a lease at the planned 80-story building. The estimated opening date is reportedly 2017. Foye said the new negotiated deal would give the Port Authority "substantial new downside protection" against a real estate market with too much available office space.

Kenneth Lipper, the deal's most outspoken critic on the Port Authority board, said a transportation agency has no business helping out a private developer with public money.

Silverstein, he said, "could put up his own buildings, he doesn't need the taxpayer to come in here and put up its money instead of building a bus station or an airport."

Scott Rechler, the board's vice chair, defended Port Authority's role in seeing a finished new World Trade Center building.

"It's our view that this project getting built has a tremendous amount of benefits to lower Manhattan and a tremendous amount of benefits to the Port Authority," he said, "from a financial standpoint and from completing our mission of rebuilding the World trade center site."