After being thwarted under the administration of former Mayor Thomas Menino, Fenway Center developer John Rosenthal is counting on Mayor Martin Walsh’s support to get the $550-million project off the ground this year.

"He’s been a big supporter for a very long time long before he was mayor, and it’s always seemed like a no-brainer," Rosenthal said Monday. "He just never understood why there was resistance at all."

Walsh has agreed to support Rosenthal’s request for a $4.6-million tax break to build 1.3 million square feet of commercial space and apartments above the Massachusetts Turnpike, the Boston Globe reported.

The tax break will be considered by the Boston Redevelopment Authority during its meeting Thursday. In 2012, Rosenthal had sought $7.8 million in tax breaks.

Rosenthal is seeking financing from Boston-based investment advisor Bentall Kennedy for the private funding.

"The markets have improved and I think there’s less perceived risk," Rosenthal said. "The return requirements by the capital markets are dropping a bit, because Boston’s so proven to work for this asset class, residential projects."

The project between Beacon Street and Brookline Avenue would be the first built in Boston using the air rights development process since Copley Place in 1980. Rosenthal said he will ask for an extension from the Massachusetts Department of Transportation on the air rights lease agreement, which expires in June. The terms call for a payment of $226 million over 99 years.

Rosenthal estimates the project would create 1,800 construction jobs and pay $5 million in annual property taxes.

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