A Fifth Avenue trophy tower is coming to market in a deal that will likely garner worldwide interest because of its location and tenancy.

Blackstone has hired Darcy Stacom and Bill Shanahan of CBRE to market the 26-story 717 Fifth Ave. The investment brokers had been waiting in the wings and began gathering signed confidentiality agreements starting in September, bidders told the Post.

But they could not officially start the marketing process until Jeff Sutton, the owner of the retail condominiums, passed on his right of first offer, or ROFO.

A CBRE team handles leasing at the building on the southeast corner of E. 56th St., which backs to the Sony building atrium.

The major office tenants are Merrill Lynch/Bank of America and Island Capital.

According to public documents, Blackstone owns 260,677 square feet of offices while Sutton owns the ground and second floors of 80,834 square feet plus the fourth floor of 23,128 square feet.

These measurements are from the condo documents and would be larger for leasing purposes, especially as the entire building is pegged at 468,000 square feet in CoStar data.

Sutton previously bought out minority partners and last year reduced SL Green Realty Corp.’s stake to 10.92 percent, thus revaluing his retail condo to $619 million or $5,015 per square foot.

That pricing comes from the value Sutton created by buying out other retail leases and completely re-jigging the stores to include the Armani and Dolce & Gabbana flagships, paying top dollar for the prime Plaza District location.

Based on recent comps, the office floors should sell for more than $1,000 per square foot, sources said, and some buyers might even toy with a future hotel or residential, although views are limited.

“It would be an extraordinary conversion,” said Bruce Mosler of Cushman & Wakefield, especially as the area’s luxury apartments are selling for the extraordinary price of $5,000-plus per square foot.

Under documents reviewed by The Post, Blackstone or any future office owner must first offer to sell the offices to the retail owner, who has 30 days to accept under the ROFO, and post a 10 percent deposit.

Since Sutton has passed, it must be sold for at least 95 percent of the price that was offered to Sutton at “materially similar” terms within nine months, and then closed in six months — or it must be re-offered to Sutton at the lower price and terms.

The offices were obtained by Blackstone as part of its 2006, $37.7 billion mega buy of all the Equity Office Properties.

Because of Sutton’s ROFO, it was removed from the multi-tower deal being flipped by Blackstone to the Macklowes for $7 billion, which ultimately resulted in them losing many of their buildings.

Blackstone declined comment while neither the brokers nor Sutton returned messages for comment.

Two of the city’s biggest building owners have settled an ongoing fight over another valuable condominium site.

Last night, Steve Roth’s Vornado Realty Trust paid Gary Barnett’s Extell Development $194 million for 137,000 square feet of development rights that centered on a garage that Extell leased at 225 W. 58th St.

It was to be part of the 920-foot tall 472,000 square-foot tower at 220 Central Park South, which is the equivalent of W. 59th. The pricing is $1,416 per square foot when similar air rights to be sold for the East Side Zoning are pegged to be $250 a square foot.

Vornado said construction can now begin on the tower, with unobstructed park views, designed by Robert A.M. Stern Architects.

It will block parts of the 1,550-foot tall tower Extell is building on the other side of W. 58th St. where Nordstrom’s will own and operate its first city store.

Jared Kushner has something to celebrate besides the birth of his second child, a son, on Monday night.

He and wife, Ivanka Trump, already have a girl, 2-year-old Arabella Rose.

The city’s Economic Development Corp. has chosen 20 companies — including Kushner’s Observer Media and SHoP Architects — to each get $10,000 as finalists in a city contest to promote the relocation of nonfinancial firms to Downtown Lower Manhattan.

This second round of Take the H.E.L.M.: Hire + Expand in Lower Manhattan had more than 300 entries from around the world.

EDC sponsors the program with the Lower Manhattan Development Corp. to bring more industries to the area formerly filled with finance and insurance tenants.

The new lucky 20 are rounded out by US companies Enigma, Lover.ly, Splash, SumAll, Uber NYC, Blueprint Health, HWKN (Hollwich Kushner)/Architizer, 4.0 Schools, Dinner Lab, Fabricating Partners, Startup Institute and Vidcaster.

The four international finalists are: inspire-A-crowd; NEVERBLAND; Sisense; and, Talent Garden, Zwift International.

Read more about the winners and finalists in next Tuesday’s New York Post special commercial real estate section.