ATLANTA (CBS) -- Burger King is calling for a ceasefire in the "burger wars."

The fast food chain is reaching out to McDonald's to propose a one-time, one-place collaboration that would combine the signature sandwiches of each restaurant into something unique – The McWhopper.

"All the tastiest bits of your Big Mac and our Whopper, united in one delicious, peace-loving burger," Burger King writes in an open letter that ran in newspapers Wednesday.

Burger King says it was inspired to extend the olive branch by "Peace One Day," a group pushing for an "annual day of global unity" on Sept. 21.

On that day, Burger King says it would open a pop-up restaurant with McDonald's somewhere in Atlanta to serve the McWhopper.

So far, there's been no response from McDonald's.