Amtrak is seeking a developer for a three-quarter acre site near 30th Street Station that Brandywine Realty Trust previously had in mind as the location of its so-called Cira II office tower.

Real-estate services firm Newmark Grubb Knight Frank has been engaged to issue a request for proposals for the long-term lease and development of the property at the corner of 30th Street and John F. Kennedy Boulevard, the rail operator said in a release Tuesday.

In the past, Brandywine and Amtrak had discussed using the site for a companion office project to the Radnor-based developer's nearby Cira Centre office tower.

The parcel has since been absorbed into the 30th Street Station District Plan, a decades-long proposal for 18 million square feet of development and acres of open space to be largely built over Amtrak's sprawling rail yard in the area.