The Port Authority has been seeking a broker to sublease 150,000 square feet of its upcoming 600,000 square feet of new offices at 4 World Trade Center.

But it looks like the agency may try to give back the space to Larry Silverstein, who is developing the new 2,845,000-square-foot tower at 150 Greenwich St.

To mark the completion of the 72-story skyscraper, there will be an event with the Philharmonic Orchestra on the evening of Nov. 13 and opening ceremonies the following day.

In a request for proposals due Tuesday, the PA stated it “no longer required the entire leased space” and expected to sublease up to 3 ¹/₂ floors, including all of 19 through 21 plus half of 18. Each floor is roughly 40,000 square feet. The agency said it would allow up to three subtenants per floor.

The PA is leasing the 15th through 29th floors, while the city’s Human Resources Administration is set to move from 180 Water St. into 607,000 square feet on the 30th through 43rd floors.

However, there are no other tenants signed for the 44th through 72nd stories of the Fumihiko Maki-designed tower that is so reflective it can get lost in the skyline.

With that in mind, it is unlikely that Silverstein wants to have 150,000 square feet dangling out there at what would likely be a cheaper rent, while he has 1,034,969 more feet left to fill.

In 2008, the PA signed a 30-year lease with Silverstein as part of the original deal that he give up the development at One WTC and reduce his lease payments for the land.

Insiders say a “bean counter” cooked up the sublease proposal as a way of generating revenue, and that the agency is unlikely to follow through. Instead, it may try to hand back the space to Silverstein, who isn’t likely to take too kindly to this proposal without a financial incentive.

The PA did not return a request for comment, although developer Douglas Durst, who is partners with the PA to develop and lease One WTC, did weigh in.

“In my discussions with the Port, it appears they are looking at alternative solutions and this space will not be put on the market. People thought it would be cheaper to keep other spaces than to move to those floors and the discussions are ongoing,” he said, adding, “They could give back the space.”

In other WTC news, the gleaming white marble `West’ portion of the East West Concourse that runs from the PATH station into Brookfield Place’s cool glass cube will finally open later this week.

Designed by Santiago Calatrava, the concourse was mired in architectural minutiae that threatened to delay the opening by several months.

Sources told us one of the nettlesome items was a “peg” near the ceiling and other fasteners needed to cover the joints of the side panels, which ended up requiring finely detailed fireproofing and painting.

At one point in the spring, it became obvious that each of the over 150 joints was taking eight days to complete, so a faster alternative was chosen.

“It’s great and handsome looking,” Durst said of the completed Concourse.

Tory Burch has not only leased 151 Mercer St. for a new flagship store, the designer will be getting a new five-story building of 12,500 square feet with a roof deck, subject to approvals from city Landmarks.

For the last 20 years, the rickety building was home to the MercBar, which left due to its upkeep problems, and now it needs to be razed for safety reasons.

The new project is being proposed by Glenwood Management executive Steven Swarzman, who bought it individually along with MercBar’s John McDonald for $8.5 million in December 2012.

Richard Hodos of CBRE represented the designer in the long-term deal, while the ownership was represented by Josh Strauss and Robert K. Futterman of RKF.

Hodos said that the designer’s townhouse on Madison Avenue has been so successful that they looked for three years to find a “dominant store in SoHo that would represent the brand.”

The new Beaux Arts Auction House will open in 7,500 square feet on the third floor of the Standard Motors Product Building at 37-18 Northern Boulevard in Long Island City.

Co-Founders Marc Lester and Michael Capo will soft open the space with offerings on Oct. 26.

Nicholas J. Rubicco handled leasing in-house for the building owners, Acumen Capital Partners, which had a rent of roughly $10,000 per month.