The group promoting a new waterfront stadium for the Buffalo Bills has offered $500,000 to the Niagara Frontier Transportation Authority for an exclusive option to negotiate purchase of 150 acres of outer harbor land.

But even with the Greater Buffalo Entertainment and Sports Complex firm putting money behind its offer, the NFTA is responding with a firm “no, thank you.”

“We’re going to stay the course,” NFTA Executive Director Kimberley A. Minkel said late Tuesday.

“We’re in the middle of negotiations with the City of Buffalo and the Erie Canal Harbor Development Corp. with a goal of maintaining public access.”

Minkel also said the authority cannot enter into the negotiations proposed by the group without launching a competitive bidding process.

The group, which proposes a new stadium for the Bills, a convention facility and an offshoot of Rochester’s Strong Museum, has been making a concerted effort to gain NFTA attention for its offer to buy the land – this time with half a million dollars attached.

They submitted their offer Tuesday in a letter sent by attorney Daniel L. Schoenborn.

But the NFTA has made it clear throughout the process that it has no intention of discussing a sale with the group.

It is expected that an agreement governing transfer of 384 acres of waterfront land will be negotiated soon among the authority, harbor agency and the city.